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there 's a man by the name of captain william swenson who recently was awarded the congressional medal of honor for his actions on september 8 , 2009 . on that day , a column of american and afghan troops were making their way through a part of afghanistan to help protect a group of government officials , a group of afghan government officials , who would be meeting with some local village elders . the column came under ambush , and was surrounded on three sides , and amongst many other things , captain swenson was recognized for running into live fire to rescue the wounded and pull out the dead . one of the people he rescued was a sergeant , and he and a comrade were making their way to a medevac helicopter . and what was remarkable about this day is , by sheer coincidence , one of the medevac medics happened to have a gopro camera on his helmet and captured the whole scene on camera . it shows captain swenson and his comrade bringing this wounded soldier who had received a gunshot to the neck . they put him in the helicopter , and then you see captain swenson bend over and give him a kiss before he turns around to rescue more . i saw this , and i thought to myself , where do people like that come from ? what is that ? that is some deep , deep emotion , when you would want to do that . there 's a love there , and i wanted to know why is it that i do n't have people that i work with like that ? you know , in the military , they give medals to people who are willing to sacrifice themselves so that others may gain . in business , we give bonuses to people who are willing to sacrifice others so that we may gain . we have it backwards . right ? so i asked myself , where do people like this come from ? and my initial conclusion was that they 're just better people . that 's why they 're attracted to the military . these better people are attracted to this concept of service . but that 's completely wrong . what i learned was that it 's the environment , and if you get the environment right , every single one of us has the capacity to do these remarkable things , and more importantly , others have that capacity too . i 've had the great honor of getting to meet some of these , who we would call heroes , who have put themselves and put their lives at risk to save others , and i asked them , `` why would you do it ? why did you do it ? '' and they all say the same thing : `` because they would have done it for me . '' it 's this deep sense of trust and cooperation . so trust and cooperation are really important here . the problem with concepts of trust and cooperation is that they are feelings , they are not instructions . i ca n't simply say to you , `` trust me , '' and you will . i ca n't simply instruct two people to cooperate , and they will . it 's not how it works . it 's a feeling . so where does that feeling come from ? if you go back 50,000 years to the paleolithic era , to the early days of homo sapiens , what we find is that the world was filled with danger , all of these forces working very , very hard to kill us . nothing personal . whether it was the weather , lack of resources , maybe a saber-toothed tiger , all of these things working to reduce our lifespan . and so we evolved into social animals , where we lived together and worked together in what i call a circle of safety , inside the tribe , where we felt like we belonged . and when we felt safe amongst our own , the natural reaction was trust and cooperation . there are inherent benefits to this . it means i can fall asleep at night and trust that someone from within my tribe will watch for danger . if we do n't trust each other , if i do n't trust you , that means you wo n't watch for danger . bad system of survival . the modern day is exactly the same thing . the world is filled with danger , things that are trying to frustrate our lives or reduce our success , reduce our opportunity for success . it could be the ups and downs in the economy , the uncertainty of the stock market . it could be a new technology that renders your business model obsolete overnight . or it could be your competition that is sometimes trying to kill you . it 's sometimes trying to put you out of business , but at the very minimum is working hard to frustrate your growth and steal your business from you . we have no control over these forces . these are a constant , and they 're not going away . the only variable are the conditions inside the organization , and that 's where leadership matters , because it 's the leader that sets the tone . when a leader makes the choice to put the safety and lives of the people inside the organization first , to sacrifice their comforts and sacrifice the tangible results , so that the people remain and feel safe and feel like they belong , remarkable things happen . i was flying on a trip , and i was witness to an incident where a passenger attempted to board before their number was called , and i watched the gate agent treat this man like he had broken the law , like a criminal . he was yelled at for attempting to board one group too soon . so i said something . i said , `` why do you have treat us like cattle ? why ca n't you treat us like human beings ? '' and this is exactly what she said to me . she said , `` sir , if i do n't follow the rules , i could get in trouble or lose my job . '' all she was telling me is that she does n't feel safe . all she was telling me is that she does n't trust her leaders . the reason we like flying southwest airlines is not because they necessarily hire better people . it 's because they do n't fear their leaders . you see , if the conditions are wrong , we are forced to expend our own time and energy to protect ourselves from each other , and that inherently weakens the organization . when we feel safe inside the organization , we will naturally combine our talents and our strengths and work tirelessly to face the dangers outside and seize the opportunities . the closest analogy i can give to what a great leader is , is like being a parent . if you think about what being a great parent is , what do you want ? what makes a great parent ? we want to give our child opportunities , education , discipline them when necessary , all so that they can grow up and achieve more than we could for ourselves . great leaders want exactly the same thing . they want to provide their people opportunity , education , discipline when necessary , build their self-confidence , give them the opportunity to try and fail , all so that they could achieve more than we could ever imagine for ourselves . charlie kim , who 's the ceo of a company called next jump in new york city , a tech company , he makes the point that if you had hard times in your family , would you ever consider laying off one of your children ? we would never do it . then why do we consider laying off people inside our organization ? charlie implemented a policy of lifetime employment . if you get a job at next jump , you can not get fired for performance issues . in fact , if you have issues , they will coach you and they will give you support , just like we would with one of our children who happens to come home with a c from school . it 's the complete opposite . this is the reason so many people have such a visceral hatred , anger , at some of these banking ceos with their disproportionate salaries and bonus structures . it 's not the numbers . it 's that they have violated the very definition of leadership . they have violated this deep-seated social contract . we know that they allowed their people to be sacrificed so they could protect their own interests , or worse , they sacrificed their people to protect their own interests . this is what so offends us , not the numbers . would anybody be offended if we gave a $ 150 million bonus to gandhi ? how about a $ 250 million bonus to mother teresa ? do we have an issue with that ? none at all . none at all . great leaders would never sacrifice the people to save the numbers . they would sooner sacrifice the numbers to save the people . bob chapman , who runs a large manufacturing company in the midwest called barry-wehmiller , in 2008 was hit very hard by the recession , and they lost 30 percent of their orders overnight . now in a large manufacturing company , this is a big deal , and they could no longer afford their labor pool . they needed to save 10 million dollars , so , like so many companies today , the board got together and discussed layoffs . and bob refused . you see , bob does n't believe in head counts . bob believes in heart counts , and it 's much more difficult to simply reduce the heart count . and so they came up with a furlough program . every employee , from secretary to ceo , was required to take four weeks of unpaid vacation . they could take it any time they wanted , and they did not have to take it consecutively . but it was how bob announced the program that mattered so much . he said , it 's better that we should all suffer a little than any of us should have to suffer a lot , and morale went up . they saved 20 million dollars , and most importantly , as would be expected , when the people feel safe and protected by the leadership in the organization , the natural reaction is to trust and cooperate . and quite spontaneously , nobody expected , people started trading with each other . those who could afford it more would trade with those who could afford it less . people would take five weeks so that somebody else only had to take three . leadership is a choice . it is not a rank . i know many people at the seniormost levels of organizations who are absolutely not leaders . they are authorities , and we do what they say because they have authority over us , but we would not follow them . and i know many people who are at the bottoms of organizations who have no authority and they are absolutely leaders , and this is because they have chosen to look after the person to the left of them , and they have chosen to look after the person to the right of them . this is what a leader is . i heard a story of some marines who were out in theater , and as is the marine custom , the officer ate last , and he let his men eat first , and when they were done , there was no food left for him . and when they went back out in the field , his men brought him some of their food so that he may eat , because that 's what happens . we call them leaders because they go first . we call them leaders because they take the risk before anybody else does . we call them leaders because they will choose to sacrifice so that their people may be safe and protected and so their people may gain , and when we do , the natural response is that our people will sacrifice for us . they will give us their blood and sweat and tears to see that their leader 's vision comes to life , and when we ask them , `` why would you do that ? why would you give your blood and sweat and tears for that person ? '' they all say the same thing : `` because they would have done it for me . '' and is n't that the organization we would all like to work in ? thank you very much . thank you . ( applause ) thank you . ( applause )

we want to give our child opportunities , education , discipline them when necessary , all so that they can grow up and achieve more than we could for ourselves . great leaders want exactly the same thing . they want to provide their people opportunity , education , discipline when necessary , build their self-confidence , give them the opportunity to try and fail , all so that they could achieve more than we could ever imagine for ourselves .

do you consider yourself a great leader ? what advice can you give to others hoping to be great leaders ?

it 's a good day to be a pirate . amaro and his four mateys , bart , charlotte , daniel , and eliza have struck gold : a chest with 100 coins . but now , they must divvy up the booty according to the pirate code . as captain , amaro gets to propose how to distribute the coins . then , each pirate , including amaro himself , gets to vote either yarr or nay . if the vote passes , or if there 's a tie , the coins are divided according to plan . but if the majority votes nay , amaro must walk the plank and bart becomes captain . then , bart gets to propose a new distribution and all remaining pirates vote again . if his plan is rejected , he walks the plank , too , and charlotte takes his place . this process repeats , with the captain 's hat moving to daniel and then eliza until either a proposal is accepted or there 's only one pirate left . naturally , each pirate wants to stay alive while getting as much gold as possible . but being pirates , none of them trust each other , so they ca n't collaborate in advance . and being blood-thirsty pirates , if anyone thinks they 'll end up with the same amount of gold either way , they 'll vote to make the captain walk the plank just for fun . finally , each pirate is excellent at logical deduction and knows that the others are , too . what distribution should amaro propose to make sure he lives ? pause here if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 if we follow our intuition , it seems like amaro should try to bribe the other pirates with most of the gold to increase the chances of his plan being accepted . but it turns out he can do much better than that . why ? like we said , the pirates all know each other to be top-notch logicians . so when each votes , they wo n't just be thinking about the current proposal , but about all possible outcomes down the line . and because the rank order is known in advance , each can accurately predict how the others would vote in any situation and adjust their own votes accordingly . because eliza 's last , she has the most outcomes to consider , so let 's start by following her thought process . she 'd reason this out by working backwards from the last possible scenario with only her and daniel remaining . daniel would obviously propose to keep all the gold and eliza 's one vote would not be enough to override him , so eliza wants to avoid this situation at all costs . now we move to the previous decision point with three pirates left and charlotte making the proposal . everyone knows that if she 's outvoted , the decision moves to daniel , who will then get all the gold while eliza gets nothing . so to secure eliza 's vote , charlotte only needs to offer her slightly more than nothing , one coin . since this ensures her support , charlotte does n't need to offer daniel anything at all . what if there are four pirates ? as captain , bart would still only need one other vote for his plan to pass . he knows that daniel would n't want the decision to pass to charlotte , so he would offer daniel one coin for his support with nothing for charlotte or eliza . now we 're back at the initial vote with all five pirates standing . having considered all the other scenarios , amaro knows that if he goes overboard , the decision comes down to bart , which would be bad news for charlotte and eliza . so he offers them one coin each , keeping 98 for himself . bart and daniel vote nay , but charlotte and eliza grudgingly vote yarr knowing that the alternative would be worse for them . the pirate game involves some interesting concepts from game theory . one is the concept of common knowledge where each person is aware of what the others know and uses this to predict their reasoning . and the final distribution is an example of a nash equilibrium where each player knows every other players ' strategy and chooses theirs accordingly . even though it may lead to a worse outcome for everyone than cooperating would , no individual player can benefit by changing their strategy . so it looks like amaro gets to keep most of the gold , and the other pirates might need to find better ways to use those impressive logic skills , like revising this absurd pirate code .

daniel would obviously propose to keep all the gold and eliza 's one vote would not be enough to override him , so eliza wants to avoid this situation at all costs . now we move to the previous decision point with three pirates left and charlotte making the proposal . everyone knows that if she 's outvoted , the decision moves to daniel , who will then get all the gold while eliza gets nothing .

what happens if a proposal is voted down ?

how is it that so many intergalactic species in movies and tv just happen to speak perfect english ? the short answer is that no one wants to watch a starship crew spend years compiling an alien dictionary . but to keep things consistent , the creators of star trek and other science-fiction worlds have introduced the concept of a universal translator , a portable device that can instantly translate between any languages . so is a universal translator possible in real life ? we already have many programs that claim to do just that , taking a word , sentence , or entire book in one language and translating it into almost any other , whether it 's modern english or ancient sanskrit . and if translation were just a matter of looking up words in a dictionary , these programs would run circles around humans . the reality , however , is a bit more complicated . a rule-based translation program uses a lexical database , which includes all the words you 'd find in a dictionary and all grammatical forms they can take , and set of rules to recognize the basic linguistic elements in the input language . for a seemingly simple sentence like , `` the children eat the muffins , '' the program first parses its syntax , or grammatical structure , by identifying the children as the subject , and the rest of the sentence as the predicate consisting of a verb `` eat , '' and a direct object `` the muffins . '' it then needs to recognize english morphology , or how the language can be broken down into its smallest meaningful units , such as the word muffin and the suffix `` s , '' used to indicate plural . finally , it needs to understand the semantics , what the different parts of the sentence actually mean . to translate this sentence properly , the program would refer to a different set of vocabulary and rules for each element of the target language . but this is where it gets tricky . the syntax of some languages allows words to be arranged in any order , while in others , doing so could make the muffin eat the child . morphology can also pose a problem . slovene distinguishes between two children and three or more using a dual suffix absent in many other languages , while russian 's lack of definite articles might leave you wondering whether the children are eating some particular muffins , or just eat muffins in general . finally , even when the semantics are technically correct , the program might miss their finer points , such as whether the children `` mangiano '' the muffins , or `` divorano '' them . another method is statistical machine translation , which analyzes a database of books , articles , and documents that have already been translated by humans . by finding matches between source and translated text that are unlikely to occur by chance , the program can identify corresponding phrases and patterns , and use them for future translations . however , the quality of this type of translation depends on the size of the initial database and the availability of samples for certain languages or styles of writing . the difficulty that computers have with the exceptions , irregularities and shades of meaning that seem to come instinctively to humans has led some researchers to believe that our understanding of language is a unique product of our biological brain structure . in fact , one of the most famous fictional universal translators , the babel fish from `` the hitchhiker 's guide to the galaxy '' , is not a machine at all but a small creature that translates the brain waves and nerve signals of sentient species through a form of telepathy . for now , learning a language the old fashioned way will still give you better results than any currently available computer program . but this is no easy task , and the sheer number of languages in the world , as well as the increasing interaction between the people who speak them , will only continue to spur greater advances in automatic translation . perhaps by the time we encounter intergalactic life forms , we 'll be able to communicate with them through a tiny gizmo , or we might have to start compiling that dictionary , after all .

finally , even when the semantics are technically correct , the program might miss their finer points , such as whether the children `` mangiano '' the muffins , or `` divorano '' them . another method is statistical machine translation , which analyzes a database of books , articles , and documents that have already been translated by humans . by finding matches between source and translated text that are unlikely to occur by chance , the program can identify corresponding phrases and patterns , and use them for future translations .

what do you think are the pros and cons of a `` statistical machine translation '' ?

after the french revolution erupted in 1789 , europe was thrown into chaos . neighboring countries ' monarchs feared they would share the fate of louis xvi , and attacked the new republic , while at home , extremism and mistrust between factions lead to bloodshed . in the midst of all this conflict , a powerful figure emerged to take charge of france . but did he save the revolution or destroy it ? `` order , order , who 's the defendant today ? i do n't see anyone . '' `` your honor , this is napoléon bonaparte , the tyrant who invaded nearly all of europe to compensate for his personal stature-based insecurities . '' `` actually , napoléon was at least average height for his time . the idea that he was short comes only from british wartime propaganda . and he was no tyrant . he was safeguarding the young republic from being crushed by the european monarchies . '' `` by overthrowing its government and seizing power himself ? '' `` your honor , as a young and successful military officer , napoléon fully supported the french revolution , and its ideals of liberty , equality , and fraternity . but the revolutionaries were incapable of real leadership . robespierre and the jacobins who first came to power unleashed a reign of terror on the population , with their anti-catholic extremism and nonstop executions of everyone who disagreed with them . and the directory that replaced them was an unstable and incompetent oligarchy . they needed a strong leader who could govern wisely and justly . '' `` so , france went through that whole revolution just to end up with another all-powerful ruler ? '' `` not quite . napoléon 's new powers were derived from the constitution that was approved by a popular vote in the consulate . '' `` ha ! the constitution was practically dictated at gunpoint in a military coup , and the public only accepted the tyrant because they were tired of constant civil war . '' `` be that as it may , napoléon introduced a new constitution and a legal code that kept some of the most important achievements of the revolution in tact : freedom of religion abolition of hereditary privilege , and equality before the law for all men . '' `` all men , indeed . he deprived women of the rights that the revolution had given them and even reinstated slavery in the french colonies . haiti is still recovering from the consequences centuries later . what kind of equality is that ? '' `` the only kind that could be stably maintained at the time , and still far ahead of france 's neighbors . '' `` speaking of neighbors , what was with all the invasions ? '' `` great question , your honor . '' `` which invasions are we talking about ? it was the neighboring empires who had invaded france trying to restore the monarchy , and prevent the spread of liberty across europe , twice by the time napoléon took charge . having defended france as a soldier and a general in those wars , he knew that the best defense is a good offense . '' `` an offense against the entire continent ? peace was secured by 1802 , and other european powers recognized the new french regime . but bonaparte could n't rest unless he had control of the whole continent , and all he knew was fighting . he tried to enforce a european-wide blockade of britain , invaded any country that did n't comply , and launched more wars to hold onto his gains . and what was the result ? millions dead all over the continent , and the whole international order shattered . '' `` you forgot the other result : the spread of democratic and liberal ideals across europe . it was thanks to napoléon that the continent was reshaped from a chaotic patchwork of fragmented feudal and religious territories into efficient , modern , and secular nation states where the people held more power and rights than ever before . '' `` should we also thank him for the rise of nationalism and the massive increase in army sizes ? you can see how well that turned out a century later . '' `` so what would european history have been like if it were n't for napoléon ? '' `` unimaginably better/worse . '' napoléon seemingly unstoppable momentum would die in the russian winter snows , along with most of his army . but even after being deposed and exiled , he refused to give up , escaping from his prison and launching a bold attempt at restoring his empire before being defeated for the second and final time . bonaparte was a ruler full of contradictions , defending a popular revolution by imposing absolute dictatorship , and spreading liberal ideals through imperial wars , and though he never achieved his dream of conquering europe , he undoubtedly left his mark on it , for better or for worse .

after the french revolution erupted in 1789 , europe was thrown into chaos . neighboring countries ' monarchs feared they would share the fate of louis xvi , and attacked the new republic , while at home , extremism and mistrust between factions lead to bloodshed .

which of the following is not a legacy attributed to napoleon ?

during a long day spent roaming the forest in search of edible grains and herbs , the weary divine farmer shennong accidentally poisoned himself 72 times . but before the poisons could end his life , a leaf drifted into his mouth . he chewed on it and it revived him , and that is how we discovered tea . or so an ancient legend goes at least . tea does n't actually cure poisonings , but the story of shennong , the mythical chinese inventor of agriculture , highlights tea 's importance to ancient china . archaeological evidence suggests tea was first cultivated there as early as 6,000 years ago , or 1,500 years before the pharaohs built the great pyramids of giza . that original chinese tea plant is the same type that 's grown around the world today , yet it was originally consumed very differently . it was eaten as a vegetable or cooked with grain porridge . tea only shifted from food to drink 1,500 years ago when people realized that a combination of heat and moisture could create a complex and varied taste out of the leafy green . after hundreds of years of variations to the preparation method , the standard became to heat tea , pack it into portable cakes , grind it into powder , mix with hot water , and create a beverage called muo cha , or matcha . matcha became so popular that a distinct chinese tea culture emerged . tea was the subject of books and poetry , the favorite drink of emperors , and a medium for artists . they would draw extravagant pictures in the foam of the tea , very much like the espresso art you might see in coffee shops today . in the 9th century during the tang dynasty , a japanese monk brought the first tea plant to japan . the japanese eventually developed their own unique rituals around tea , leading to the creation of the japanese tea ceremony . and in the 14th century during the ming dynasty , the chinese emperor shifted the standard from tea pressed into cakes to loose leaf tea . at that point , china still held a virtual monopoly on the world 's tea trees , making tea one of three essential chinese export goods , along with porcelain and silk . this gave china a great deal of power and economic influence as tea drinking spread around the world . that spread began in earnest around the early 1600s when dutch traders brought tea to europe in large quantities . many credit queen catherine of braganza , a portuguese noble woman , for making tea popular with the english aristocracy when she married king charles ii in 1661 . at the time , great britain was in the midst of expanding its colonial influence and becoming the new dominant world power . and as great britain grew , interest in tea spread around the world . by 1700 , tea in europe sold for ten times the price of coffee and the plant was still only grown in china . the tea trade was so lucrative that the world 's fastest sailboat , the clipper ship , was born out of intense competition between western trading companies . all were racing to bring their tea back to europe first to maximize their profits . at first , britain paid for all this chinese tea with silver . when that proved too expensive , they suggested trading tea for another substance , opium . this triggered a public health problem within china as people became addicted to the drug . then in 1839 , a chinese official ordered his men to destroy massive british shipments of opium as a statement against britain 's influence over china . this act triggered the first opium war between the two nations . fighting raged up and down the chinese coast until 1842 when the defeated qing dynasty ceded the port of hong kong to the british and resumed trading on unfavorable terms . the war weakened china 's global standing for over a century . the british east india company also wanted to be able to grow tea themselves and further control the market . so they commissioned botanist robert fortune to steal tea from china in a covert operation . he disguised himself and took a perilous journey through china 's mountainous tea regions , eventually smuggling tea trees and experienced tea workers into darjeeling , india . from there , the plant spread further still , helping drive tea 's rapid growth as an everyday commodity . today , tea is the second most consumed beverage in the world after water , and from sugary turkish rize tea , to salty tibetan butter tea , there are almost as many ways of preparing the beverage as there are cultures on the globe .

at that point , china still held a virtual monopoly on the world 's tea trees , making tea one of three essential chinese export goods , along with porcelain and silk . this gave china a great deal of power and economic influence as tea drinking spread around the world . that spread began in earnest around the early 1600s when dutch traders brought tea to europe in large quantities .

it was with the expanding influence of british empire that tea became widely popular in many cultures in a short period of time . what other examples do we have of seeing a direction of cultural influence correlates with influence of power and economy ?

how did dracula become the world 's most famous vampire ? more than 100 years after his creator was laid to rest , dracula lives on as the most famous vampire in history . but this transylvanian noble , neither the first fictional vampire nor the most popular of his time , may have remained buried in obscurity if not for a twist of fate . dracula 's first appearance was in bram stoker 's 1897 novel of the same name . but that was far from the beginning of vampire myths . blood-sucking monsters had already been part of folklore for at least 800 years . it was slavic folklore that gave us the word vampire , or `` upir '' in old russian . the term 's first known written mention comes from the 11th century . vampire lore in the region predated christianity 's arrival and persisted despite the church 's efforts to eliminate pagan beliefs . stories of vampires originated from misinterpretations of diseases , such as rabies , and pellagra , and decomposition . in the case of the latter , gasses swelling the body and blood oozing from the mouth could make a corpse look like it had recently been alive and feeding . vampires were describe as bloated with overgrown teeth and nails . this gave rise to many rituals intended to prevent the dead from rising , such as burying bodies with garlic or poppyseeds , as well as having them staked , burned , or mutilated . vampire lore remained a local phenomenon until the 18th century when serbia was caught in the struggle between two great powers , the habsburg monarchy and ottoman empire . austrian soldiers and government officials observed and documented the strange local burial rituals , and their reports became widely publicized . the resulting vampire hysteria got so out of hand that in 1755 , the austrian empress was forced to dispatch her personal physician . he investigated and put an end to the rumors by publishing a thorough , scientific refutation . the panic subsided , but the vampire had already taken root in western europe 's imagination , spawning works like `` the vampyre '' in 1819 , and joseph sheridan le fanu 's `` carmilla '' in 1872 . this book would greatly influence a young irish drama critic named bram stoker . stoker , who was born in dublin in 1847 , was famously bedridden with an unknown illness until the age of seven . during that time , his mother told him folktales and true tales of horror , including her experiences during an outbreak of cholera in 1832 . there , she described victims buried alive in mass graves . later in his life , stoker went on to write fantasy , romance , adventure stories , and , in 1897 , `` dracula . '' although the book 's main villain and namesake is thought to be based on the historical figure of vlad iii dracula , or vlad the impaler , the association is mostly just that they share a name . other elements and characters were inspired directly and indirectly by various works in the victorian era , such as `` the mysterious stranger . '' the novel , upon release , was only a moderate success in its day , nor was it even stoker 's most well-known work , mentioned only briefly in a 1912 obituary . but a critical copyright battle would completely change dracula 's fate , and catapult the character into literary renown . in 1922 , a german studio adapted the novel into the now classic silent film `` nosferatu '' without paying royalties . despite changes in character names and minor plot points , the parallels were obvious , and the studio was sued into bankruptcy . to prevent more plagiarism attempts , stoker 's widow decided to establish copyright over the stage version of `` dracula '' by approving a production by family-friend hamilton deane . although deane 's adaptation made drastic cuts to the story , it became a classic , thanks largely to bela lugosi 's performance on broadway . lugosi would go on to star in the 1931 film version by universal , lending the character many of his signature characteristics . and since then , dracula has risen again in countless adaptations , finding eternal life far beyond the humble pages of his birth .

there , she described victims buried alive in mass graves . later in his life , stoker went on to write fantasy , romance , adventure stories , and , in 1897 , `` dracula . '' although the book 's main villain and namesake is thought to be based on the historical figure of vlad iii dracula , or vlad the impaler , the association is mostly just that they share a name .

bram stoker was not only a writer of horror . he also wrote fantasy , adventure , and ______ .

jean-paul sartre made thinking and philosophy glamorous . he was born in paris in 1905 . his father , a navy captain , died when he was a baby – and he grew up extremely close to his mother until she remarried , much to his regret , when he was twelve . sartre spent most of his life in paris , where he often went to cafes on the left bank . he had a strabismus , a wandering eye , and wore distinctive , heavy glasses . he was very short ( five feet three inches ) and frequently described himself as ugly . by the 60 ’ s sartre was a household name in both europe and the united states , and so was his chosen philosophy , existentialism . sartre is famous principally for his book being and nothingness ( 1943 ) , which enhanced his reputation not so much because people could understand his ideas but because they could n't quite . existentialism was built around a number of key insights : one : things are weirder than we think sartre is acutely attentive to moments when the world reveals itself as far stranger and more uncanny than we normally admit ; moments when the logic we ascribe to it day-to-day becomes unavailable , showing things to be highly contingent and even absurd and frightening . sartre ’ s first novel – nausea , published in 1938 – is full of evocations of such moments . at one point , the hero , roquentin , a 30-year-old writer living in a fictional french seaside town , is on a tram . he puts his hand on the seat , but then pulls it back rapidly . instead of being the most basic and obvious piece of design , scarcely worth a moment ’ s notice , the seat promptly strikes him as deeply strange ; the word ‘ seat ’ comes loose from its moorings , the object it refers to shines forth in all its primordial oddity , as if he ’ s never seen one before . roquentin has to force himself to remember that this thing beside him is something for people to sit on . for a terrifying moment , roquentin has peered into what sartre calls the ‘ absurdity of the world. ’ such a moment goes to the heart of sartre ’ s philosophy . to be sartrean is to be aware of existence as it is when it has been stripped of any of the prejudices and stabilising assumptions lent to us by our day-to-day routines . we can try out a sartrean perspective on many aspects of our own lives . think of what you know as ‘ the evening meal with your partner ’ . under such a description , it all seems fairly logical , but a sartrean would strip away the surface normality to show the radical strangeness lurking beneath . dinner really means that : when your part of the planet has spun away from the energy of a distant hydrogen and helium explosion , you slide your knees under strips of a chopped-up tree and put sections of dead animals and plants in your mouth and chew , while next to you , another mammal whose genitals you sometimes touch is doing the same . two : we are free such weird moments are certainly disorienting and rather scary , but sartre wants to draw our attention to them for one central reason : because of their liberating dimensions . life is a lot odder than we think , but it ’ s also as a consequence far richer in possibilities . things don ’ t have to be quite the way they are . in the course of fully realising our freedom , we will come up against what sartre calls the ‘ angoisse ’ or ‘ anguish ’ of existence . everything is ( terrifyingly ) possible because nothing has any pre-ordained , god-given sense or purpose . humans are just making it up as they go along , and are free to cast aside the shackles at any moment . three : we shouldn ’ t live in ‘ bad faith ’ sartre gave a term to the phenomenon of living without taking freedom properly on board . he called it bad faith . we are in bad faith whenever we tell ourselves that things have to be a certain way and shut our eyes to other options . it is bad faith to insist that we have to do a particular kind of work or live with a specific person or make our home in a given place . the most famous description of ‘ bad faith ’ comes in being and nothingness , when sartre notices a waiter who strikes him as overly devoted to his role , as if he were first and foremost a waiter rather than a free human being . his movement is quick and forward , a little too precise , a little too rapid . he comes towards the patrons with a step that is a little too quick . he bends forward a little too eagerly : his voice , his eyes express an interest a little too solicitous for the order of the customer… ’ the man ( he was probably modelled on someone in saint-germain ’ s café de flore ) has convinced himself that he is essentially , necessarily a waiter rather than a free creature who could be a jazz pianist or a fisherman on a north sea trawler . four : we 're free to dismantle capitalism . the one factor that most discourages people from experiencing themselves as free is money . most of us will shut down a range of possible options ( moving abroad , trying out a new career , leaving a partner ) by saying , ‘ that ’ s if i didn ’ t have to worry about money . ' this passivity in the face of money enraged sartre at a political level . he thought of capitalism as a giant machine designed to create a sense of necessity which doesn ’ t in fact exist in reality : it makes us tell ourselves we have to work a certain number of hours , buy a particular product or service , and so on . but in this , there is only the denial of freedom – and a refusal to take as seriously as we should the possibility of living in other ways . it was because of these views that sartre had a life long interest in marxism . marxism seemed in theory to allow people to explore their freedom , by reducing the role played in their lives by material considerations . sartre took part in many protests in the streets of paris in the 60s . arrested yet again in 1968 , president charles de gaulle had him pardoned , saying , “ you don ’ t arrest voltaire. ” sartre also visited fidel castro and che guevara and admired them both deeply . as a result of these connections and his radical politics , the fbi kept a large file on sartre trying to deduce what his suspicious philosophy might really mean . sartre is inspiring in his insistence that things do not have to be the way they are . he is hugely alive to our unfulfilled potential , as individuals and as a species . he urges us to accept the fluidity of existence and to create new institutions , habits , outlooks and ideas . the admission that life doesn ’ t have some preordained logic and is not inherently meaningful can be a source of immense relief when we feel oppressed by the weight of tradition and the status quo .

instead of being the most basic and obvious piece of design , scarcely worth a moment ’ s notice , the seat promptly strikes him as deeply strange ; the word ‘ seat ’ comes loose from its moorings , the object it refers to shines forth in all its primordial oddity , as if he ’ s never seen one before . roquentin has to force himself to remember that this thing beside him is something for people to sit on . for a terrifying moment , roquentin has peered into what sartre calls the ‘ absurdity of the world. ’ such a moment goes to the heart of sartre ’ s philosophy . to be sartrean is to be aware of existence as it is when it has been stripped of any of the prejudices and stabilising assumptions lent to us by our day-to-day routines .

nausea protagonist roquentin is overwhelmed by the profound absurdity of which ordinary object ?

many of us have hundreds of things on our minds at any moment , often struggling to keep track of everything we need to do . but fortunately , there 's one important thing we do n't have to worry about remembering : breathing . when you breathe , you transport oxygen to the body 's cells to keep them working and clear your system of the carbon dioxide that this work generates . breathing , in other words , keeps the body alive . so , how do we accomplish this crucial and complex task without even thinking about it ? the answer lies in our body 's respiratory system . like any machinery , it consists of specialized components , and requires a trigger to start functioning . here , the components are the structures and tissues making up the lungs , as well as the various other respiratory organs connected to them . and to get this machine moving , we need the autonomic nervous system , our brain 's unconscious control center for the vital functions . as the body prepares to take in oxygen-rich air , this system sends a signal to the muscles around your lungs , flattening the diaphragm and contracting the intercostal muscles between your ribs to create more space for the lungs to expand . air then wooshes into your nose and mouth , through your trachea , and into the bronchi that split at the trachea 's base , with one entering each lung . like tree branches , these small tubes divide into thousands of tinier passages called bronchioles . it 's tempting to think of the lungs as huge balloons , but instead of being hollow , they 're actually spongy inside , with the bronchioles running throughout the parenchyma tissue . at the end of each bronchiole is a little air sack called an alveolus , wrapped in capillaries full of red blood cells containing special proteins called hemoglobin . the air you 've breathed in fills these sacks , causing the lungs to inflate . here is where the vital exchange occurs . at this point , the capillaries are packed with carbon dioxide , and the air sacks are full of oxygen . but due to the basic process of diffusion , the molecules of each gas want to move to a place where there 's a lower concentration of their kind . so as oxygen crosses over to the capillaries , the hemoglobin grabs it up , while the carbon dioxide is unloaded into the lungs . the oxygen-rich hemoglobin is then transported throughout the body via the bloodstream . but what do our lungs do with all that carbon dioxide ? exhale it , of course . the autonomic nervous system kicks in again , causing the diaphragm to ball up , and the intercostal muscles to relax , making the chest cavities smaller and forcing the lungs to compress . the carbon dioxide-rich air is expelled , and the cycle begins again . so that 's how these spongy organs keep our bodies efficiently supplied with air . lungs inhale and exhale between 15 and 25 times a minute , which amounts to an incredible 10,000 liters of air each day . that 's a lot of work , but do n't sweat it . your lungs and your autonomic nervous system have got it covered .

the oxygen-rich hemoglobin is then transported throughout the body via the bloodstream . but what do our lungs do with all that carbon dioxide ? exhale it , of course .

what controls the movement of the lungs ?

what is love ? seriously , though , what is it ? what is love ? a verb ? a noun ? a universal truth ? an ideal ? a common thread of all religions ? a cult ? a neurological phenomenon ? there 's no shortage of answers . some are all-encompassing . it conquers all . it 's all you need . it 's all there is . these are all comparisons , though , ways of defining it by contrast , by saying it 's more important than all other things , but is it ? sure , love matters more than your standard turkey sandwich , but does it matter more than shelter ? or sanity ? or an exceptional turkey sandwich ? no matter your answer , you 're just ranking it , not defining it . another challenge to defining love is we often try to do so while falling into it or out of it . would you trust someone who just won the lottery to accurately define the concept of currency ? or , i do n't know , ask a guy to define bears while he 's fending them off ? or is romance not like winning the lottery ? are break ups not like bear attacks ? bad comparisons ? that 's my point . i 'm not thinking right because i 'm in love , so ha ! taking a step back , or taking a cold shower , whatever , love is potentially the most intensely thought about thing in all of human history . and despite centuries upon centuries of obsession , it still overwhelms us . some say it 's a feeling , a magical emotion , a feeling for someone like you 've never felt before . but feelings are fluid , not very concrete foundation for a definition . sometimes you hate the person you love . plus , come on , you 've felt feelings like it before , sort of in miniature . your relationships with your family shape your relationships with partners . and your love for your partner may be in its own dynamic relationship , healthy or totally weird , with the love of your parents and siblings . love is also a set of behaviors we associate with the feeling : holding hands , kissing , hugging , public displays of affection , dating , marriage , having kids , or just sex . but these loving actions can be subjective or culturally relative . you may love or be someone who ca n't have kids or does n't want to , who believes in marriage but also in divorce , who 's from a culture where people do n't really date the way we think of dating , or who just does n't want to make out on the bus . but if love is a thing that we can define , then how can it mean opposite things for so many people ? so , maybe love 's just all in your head , a personal mystery winding through your neural pathways and lighting up pleasing , natural rewards in your nervous system . perhaps these rewards are addictive . perhaps love is a temporary or permanent addiction to a person , just like a person can be addicted to a drug . i do n't mean to be edgy like some pop song . evidence shows that chemicals in your brain stimulated by another person can make you develop a habit for that person . the person comes to satisfy a physiological craving , and you want more . but then sometimes , slowly or suddenly , you do n't . you 've fallen out of love , become unaddicted , for a spell . what happened ? does one develop a tolerance or hit a limit ? why do some lovers stay addicted to each other their entire lives ? perhaps to create new lives , to proliferate their species ? maybe love is just human dna 's optimal method for bringing about its own replication . there are evolutionary arguments regarding every human mating behavior , from how we display ourselves to potential mates , to how we treat each other in relationships , to how we raise kids . thus , some argue that the feeling you think you feel in your soul is just biology 's way to make you continue our species . nature has selected you to have crushes on hotties , just like it makes monkeys have crushes on hot monkeys , and biology marches on . but is that all love is ? or , perhaps worse , is it just a construct , some fake concept we all convince each other to try to live up to for a fake sense of purpose ? maybe it is a construct , but let 's be more precise about what a construct is because love is constructed from reality : our experiences , feelings , brain chemistry , cultural expectations , our lives . and this edifice can be viewed through countless dimensions : scientific , emotional , historical , spiritual , legal , or just personal . if no two people are the same , no two people 's love is the same either . so , in every loving relationship , there 's a lot to talk about and partners should be open to that , or the relationship probably wo n't last . love is always up for discussion and , sure , under construction . so , if we ca n't define it , that 's a good sign . it means we 're all still making it . wait , i did n't mean , you know what i meant .

what is love ? seriously , though , what is it ?

one theory is that love is a subconscious means to :

maybe you 've recently seen the phrase `` gluten-free '' on food packaging , or take-out menus , shampoo bottles , apartment listings , the tag of your shirt , on a hammer , as a lower back tattoo , or in your friend 's resume . next time someone starts telling you about their newfound freedom from gluten , here are some questions you can ask , and the well-informed answers that your friend , being a reasonable individual making educated dietary choices , and by no means just following the latest diet craze , will tell you . what is gluten ? gluten is an insoluble protein composite made up of two proteins named gliadin and glutenin . where might you encounter gluten ? gluten is found in certain grains , particularly wheat , rye and barley . what has gluten been doing for the previous entirety of human history , and why do you suddenly care about it ? gluten is responsible for the elastic consistency of dough and the chewiness of foods made from wheat flour , like bread and pasta . for some people , these foods cause problems , namely wheat allergy , celiac disease , and non-celiac gluten sensitivity . wheat allergy is an uncommon condition that occurs when a person 's immune system mounts an allergic response to wheat proteins , leading to mild problems , and in rare cases , a potential dangerous reaction called anaphylaxis . celiac disease is an inherited disease , in which eating foods with gluten leads to inflammation and damage of the lining of the small intestine . this impairs intestinal function , leading to problems like belly pain , bloating , gas , diarrhea , weight loss , skin rash , bone problems like osteoporosis , iron deficiency , small stature , infertility , fatigue and depression . untreated , celiac disease increases the risk of developing certain types of cancer . celiac disease is present in one in every 100 to 200 persons in the u.s . when blood tests suggest the possibility of celiac , the diagnosis is confirmed with a biopsy . the most effective treatment is a gluten-free diet , which helps heal intestinal damage and improve symptoms . some people do n't have celiac disease or a wheat allergy , but still experience symptoms when they eat foods with gluten . these people have non-celiac gluten sensitivity . they experience painful gut symptoms and suffer from fatigue , brain fog , joint pain or skin rash . a gluten-free diet typically helps with these symptoms . so how many people actually have this gluten sensitivity you speak of ? gluten sensitivity 's occurrence in the general population is unclear , but likely much more common than wheat allergy or celiac disease . diagnosis is based on the development of symptoms , the absence of wheat allergy and celiac disease , and subsequent improvement on a gluten-free diet . there 's no reliable blood or tissue test , partly because gluten sensitivity is n't a single disease , and has a number of different possible causes . for example , it may be the case that gluten can activate the immune system in the small intestine , or cause it to become leaky . but sometimes , people claiming gluten sensitivity are actually sensitive not to wheat proteins , but sugars found in wheat and other foods , called fructans . the human intestine ca n't break down or absorb fructans , so they make their way to the large intestine or colon , where they 're fermented by bacteria , producing short-chain fatty acids and gases . this leads to unpleasant symptoms in some people with bowel problems . another possible explanation behind gluten sensitivity is the nocebo effect . this occurs when a person believes something will cause problems , and because of that belief , it does . it 's the opposite of the more well-known and much more fortuitous placebo effect . given how much bad press gluten is getting in the media , the nocebo response may play a role for some people who think they 're sensitive to gluten . for all these reasons , it 's clear that the problems people develop when they eat wheat and other grains are n't exclusively due to gluten . so a better name than non-celiac gluten sensitivty might be wheat intolerance .

they experience painful gut symptoms and suffer from fatigue , brain fog , joint pain or skin rash . a gluten-free diet typically helps with these symptoms . so how many people actually have this gluten sensitivity you speak of ?

your friend tells you she is on a gluten-free diet . you want to take her out for a birthday dinner . what might the menu consist of ? ( be sure to meet her dietary needs without causing her stomach issues ! )

translator : andrea mcdonough reviewer : bedirhan cinar a couple of years ago i started using twitter , and one of the things that really charmed me about twitter is that people would wake up in the morning and they would say , `` good morning ! '' which i thought , i 'm a canadian , so i was a little bit , i liked that politeness . and so , i 'm also a giant nerd , and so i wrote a computer program that would record 24 hours of everybody on twitter saying , `` good morning ! '' and then i asked myself my favorite question , `` what would that look like ? '' well , as it turns out , i think it would look something like this . right , so we 'd see this wave of people saying , `` good morning ! '' across the world as they wake up . now the green people , these are people that wake up at around 8 o'clock in the morning , who wakes up at 8 o'clock or says , `` good morning ! '' at 8 ? and the orange people , they say , `` good morning ! '' around 9 . and the red people , they say , `` good morning ! '' around 10 . yeah , more at 10 's than , more at 10 's than 8 's . and actually if you look at this map , we can learn a little bit about how people wake up in different parts of the world . people on the west coast , for example , they wake up a little bit later than those people on the east coast . but that 's not all that people say on twitter , right ? we also get these really important tweets , like , `` i just landed in orlando ! ! [ plane sign , plane sign ] '' or , or , `` i just landed in texas [ exclamation point ] ! '' or `` i just landed in honduras ! '' these lists , they go on and on and on , all these people , right ? so , on the outside , these people are just telling us something about how they 're traveling . but we know the truth , do n't we ? these people are show-offs ! they are showing off that they 're in cape town and i 'm not . so i thought , how can we take this vanity and turn it into utility ? so using a similar approach that i did with `` good morning , '' i mapped all those people 's trips because i know where they 're landing , they just told me , and i know where they live because they share that information on their twitter profile . so what i 'm able to do with 36 hours of twitter is create a model of how people are traveling around the world during that 36 hours . and this is kind of a prototype because i think if we listen to everybody on twitter and facebook and the rest of our social media , we 'd actually get a pretty clear picture of how people are traveling from one place to the other , which is actually turns out to be a very useful thing for scientists , particularly those who are studying how disease is spread . so , i work upstairs in the new york times , and for the last two years , we 've been working on a project called , `` cascade , '' which in some ways is kind of similar to this one . but instead of modeling how people move , we 're modeling how people talk . we 're looking at what does a discussion look like . well , here 's an example . this is a discussion around an article called , `` the island where people forget to die '' . it 's about an island in greece where people live a really , really , really , really , really , really long time . and what we 're seeing here is we 're seeing a conversation that 's stemming from that first tweet down in the bottom , left-hand corner . so we get to see the scope of this conversation over about 9 hours right now , we 're going to creep up to 12 hours here in a second . but , we can also see what that conversation looks like in three dimensions . and that three-dimensional view is actually much more useful for us . as humans , we are really used to things that are structured as three dimensions . so , we can look at those little off-shoots of conversation , we can find out what exactly happened . and this is an interactive , exploratory tool so we can go through every step in the conversation . we can look at who the people were , what they said , how old they are , where they live , who follows them , and so on , and so on , and so on . so , the times creates about 6,500 pieces of content every month , and we can model every single one of the conversations that happen around them . and they look somewhat different . depending on the story and depending on how fast people are talking about it and how far the conversation spreads , these structures , which i call these conversational architectures , end up looking different . so , these projects that i 've shown you , i think they all involve the same thing : we can take small pieces of data and by putting them together , we can generate more value , we can do more exciting things with them . but so far we 've only talked about twitter , right ? and twitter is n't all the data . we learned a moment ago that there is tons and tons , tons more data out there . and specifically , i want you to think about one type of data because all of you guys , everybody in this audience , we , we , me as well , are data-making machines . we are producing data all the time . every single one of us , we 're producing data . somebody else , though , is storing that data . usually we put our trust into companies to store that data , but what i want to suggest here is that rather than putting our trust in companies to store that data , we should put the trust in ourselves because we actually own that data . right , that is something we should remember . everything that someone else measures about you , you actually own . so , it 's my hope , maybe because i 'm a canadian , that all of us can come together with this really valuable data that we 've been storing , and we can collectively launch that data toward some of the world 's most difficulty problems because big data can solve big problems , but i think it can do it the best if it 's all of us who are in control . thank you .

but so far we 've only talked about twitter , right ? and twitter is n't all the data . we learned a moment ago that there is tons and tons , tons more data out there .

what 's a big data project you can start ? do you think it 's possible without the use of social media platforms ( like twitter and facebook ) ?

gifts . what a wonderful thing . who can say `` no '' to them , right ? when i was six years old , i received my gifts . my first grade teacher had this brilliant idea . she wanted us to experience receiving gifts but also learning the virtue of complimenting each other . so she had all of us come to the front of the classroom , and she bought all of us gifts and stacked them in the corner . and she said , `` why do n't we just stand here and compliment each other ? if you hear your name called , go and pick up your gift and sit down . '' what a wonderful idea , right ? what could go wrong ? ( laughter ) well , there were 40 of us to start with , and every time i heard someone 's name called , i would give out the heartiest cheer . and then there were 20 people left , and 10 people left , and five left ... and three left . and i was one of them . and the compliments stopped . well , at that moment , i was crying . and i did n't want to hear `` gifts '' anymore . i did n't want compliments anymore , i just wanted to get out of there and sit down . and the teacher was freaking out . she was like , `` hey , would anyone say anything nice about these people ? '' ( laughter ) `` no one ? ok , why do n't you go get your gift and sit down . so behave next year -- someone might say something nice about you . '' ( laughter ) well , as i 'm describing this you , you probably know i remember this really well . ( laughter ) but i do n't know who felt worse that day . was it me or the teacher ? she must have realized that she turned a team-building event into a public roast for three six-year-olds . and without the humor . you know , when you see people get roasted on tv , it was funny . there was nothing funny about that day . so that was one version of me , and i would die to avoid being in that situation again -- to get rejected in public again . that 's one version . then fast-forward eight years . bill gates came to my hometown -- beijing , china -- to speak , and i saw his message . i fell in love with that guy . i thought , wow , i know what i want to do now . that night i wrote a letter to my family telling them : `` by age 25 , i will build the biggest company in the world , and that company will buy microsoft . '' ( laughter ) i totally embraced this idea of conquering the world -- domination , right ? and i did n't make this up , i did write that letter . and here it is -- ( laughter ) you do n't have to read this through -- ( laughter ) this is also bad handwriting , but i did highlight some key words . you get the idea . ( laughter ) so ... that was another version of me : one who will conquer the world . well , then two years later , i was presented with the opportunity to come to the united states . i jumped on it , because that was where bill gates lived , right ? ( laughter ) i thought that was the start of my entrepreneur journey . then , fast-forward another 14 years . i was 30 . nope , i did n't build that company . i did n't even start . i was actually a marketing manager for a fortune 500 company . and i felt i was stuck ; i was stagnant . why is that ? where is that 14-year-old who wrote that letter ? it 's not because he did n't try . it 's because every time i had a new idea , every time i wanted to try something new , even at work -- i wanted to make a proposal , i wanted to speak up in front of people in a group -- i felt there was this constant battle between the 14-year-old and the six-year-old . one wanted to conquer the world -- make a difference -- another was afraid of rejection . and every time that six-year-old won . and this fear even persisted after i started my own company . i mean , i started my own company when i was 30 -- if you want to be bill gates , you 've got to start sooner or later , right ? when i was an entrepreneur , i was presented with an investment opportunity , and then i was turned down . and that rejection hurt me . it hurt me so bad that i wanted to quit right there . but then i thought , hey , would bill gates quit after a simple investment rejection ? would any successful entrepreneur quit like that ? no way . and this is where it clicked for me . ok , i can build a better company . i can build a better team or better product , but one thing for sure : i 've got to be a better leader . i 've got to be a better person . i can not let that six-year-old keep dictating my life anymore . i have to put him back in his place . so this is where i went online and looked for help . google was my friend . ( laughter ) i searched , `` how do i overcome the fear of rejection ? '' i came up with a bunch of psychology articles about where the fear and pain are coming from . then i came up with a bunch of `` rah-rah '' inspirational articles about `` do n't take it personally , just overcome it . '' who does n't know that ? ( laughter ) but why was i still so scared ? then i found this website by luck . it 's called rejectiontherapy.com . ( laughter ) `` rejection therapy '' was this game invented by this canadian entrepreneur . his name is jason comely . and basically the idea is for 30 days you go out and look for rejection , and every day get rejected at something , and then by the end , you desensitize yourself from the pain . and i loved that idea . ( laughter ) i said , `` you know what ? i 'm going to do this . and i 'll feel myself getting rejected 100 days . '' and i came up with my own rejection ideas , and i made a video blog out of it . and so here 's what i did . this is what the blog looked like . day one ... ( laughter ) borrow 100 dollars from a stranger . so this is where i went to where i was working . i came downstairs and i saw this big guy sitting behind a desk . he looked like a security guard . so i just approached him . and i was just walking and that was the longest walk of my life -- hair on the back of my neck standing up , i was sweating and my heart was pounding . and i got there and said , `` hey , sir , can i borrow 100 dollars from you ? '' ( laughter ) and he looked up , he 's like , `` no . '' `` why ? '' and i just said , `` no ? i 'm sorry . '' then i turned around , and i just ran . ( laughter ) i felt so embarrassed . but because i filmed myself -- so that night i was watching myself getting rejected , i just saw how scared i was . i looked like this kid in `` the sixth sense . '' i saw dead people . ( laughter ) but then i saw this guy . you know , he was n't that menacing . he was a chubby , loveable guy , and he even asked me , `` why ? '' in fact , he invited me to explain myself . and i could 've said many things . i could 've explained , i could 've negotiated . i did n't do any of that . all i did was run . i felt , wow , this is like a microcosm of my life . every time i felt the slightest rejection , i would just run as fast as i could . and you know what ? the next day , no matter what happens , i 'm not going to run . i 'll stay engaged . day two : request a `` burger refill . '' ( laughter ) it 's when i went to a burger joint , i finished lunch , and i went to the cashier and said , `` hi , can i get a burger refill ? '' ( laughter ) he was all confused , like , `` what 's a burger refill ? '' ( laughter ) i said , `` well , it 's just like a drink refill but with a burger . '' and he said , `` sorry , we do n't do burger refill , man . '' ( laughter ) so this is where rejection happened and i could have run , but i stayed . i said , `` well , i love your burgers , i love your joint , and if you guys do a burger refill , i will love you guys more . '' ( laughter ) and he said , `` well , ok , i 'll tell my manager about it , and maybe we 'll do it , but sorry , we ca n't do this today . '' then i left . and by the way , i do n't think they 've ever done burger refill . ( laughter ) i think they 're still there . but the life and death feeling i was feeling the first time was no longer there , just because i stayed engaged -- because i did n't run . i said , `` wow , great , i 'm already learning things . great . '' and then day three : getting olympic doughnuts . this is where my life was turned upside down . i went to a krispy kreme . it 's a doughnut shop in mainly the southeastern part of the united states . i 'm sure they have some here , too . and i went in , i said , `` can you make me doughnuts that look like olympic symbols ? basically , you interlink five doughnuts together ... `` i mean there 's no way they could say yes , right ? the doughnut maker took me so seriously . ( laughter ) so she put out paper , started jotting down the colors and the rings , and is like , `` how can i make this ? '' and then 15 minutes later , she came out with a box that looked like olympic rings . and i was so touched . i just could n't believe it . and that video got over five million views on youtube . the world could n't believe that either . ( laughter ) you know , because of that i was in newspapers , in talk shows , in everything . and i became famous . a lot of people started writing emails to me and saying , `` what you 're doing is awesome . '' but you know , fame and notoriety did not do anything to me . what i really wanted to do was learn , and to change myself . so i turned the rest of my 100 days of rejection into this playground -- into this research project . i wanted to see what i could learn . and then i learned a lot of things . i discovered so many secrets . for example , i found if i just do n't run , if i got rejected , i could actually turn a `` no '' into a `` yes , '' and the magic word is , `` why . '' so one day i went to a stranger 's house , i had this flower in my hand , knocked on the door and said , `` hey , can i plant this flower in your backyard ? '' ( laughter ) and he said , `` no . '' but before he could leave i said , `` hey , can i know why ? '' and he said , `` well , i have this dog that would dig up anything i put in the backyard . i do n't want to waste your flower . if you want to do this , go across the street and talk to connie . she loves flowers . '' so that 's what i did . i went across and knocked on connie 's door . and she was so happy to see me . ( laughter ) and then half an hour later , there was this flower in connie 's backyard . i 'm sure it looks better now . ( laughter ) but had i left after the initial rejection , i would 've thought , well , it 's because the guy did n't trust me , it 's because i was crazy , because i did n't dress up well , i did n't look good . it was none of those . it was because what i offered did not fit what he wanted . and he trusted me enough to offer me a referral , using a sales term . i converted a referral . then one day -- and i also learned that i can actually say certain things and maximize my chance to get a yes . so for example , one day i went to a starbucks , and asked the manager , `` hey , can i be a starbucks greeter ? '' he was like , `` what 's a starbucks greeter ? '' i said , `` do you know those walmart greeters ? you know , those people who say 'hi ' to you before you walk in the store , and make sure you do n't steal stuff , basically ? i want to give a walmart experience to starbucks customers . '' ( laughter ) well , i 'm not sure that 's a good thing , actually -- actually , i 'm pretty sure it 's a bad thing . and he was like , `` oh '' -- yeah , this is how he looked , his name is eric -- and he was like , `` i 'm not sure . '' this is how he was hearing me . `` not sure . '' then i ask him , `` is that weird ? '' he 's like , `` yeah , it 's really weird , man . '' but as soon as he said that , his whole demeanor changed . it 's as if he 's putting all the doubt on the floor . and he said , `` yeah , you can do this , just do n't get too weird . '' ( laughter ) so for the next hour i was the starbucks greeter . i said `` hi '' to every customer that walked in , and gave them holiday cheers . by the way , i do n't know what your career trajectory is , do n't be a greeter . ( laughter ) it was really boring . but then i found i could do this because i mentioned , `` is that weird ? '' i mentioned the doubt that he was having . and because i mentioned , `` is that weird ? `` , that means i was n't weird . that means i was actually thinking just like him , seeing this as a weird thing . and again , and again , i learned that if i mention some doubt people might have before i ask the question , i gained their trust . people were more likely to say yes to me . and then i learned i could fulfill my life dream ... by asking . you know , i came from four generations of teachers , and my grandma has always told me , `` hey jia , you can do anything you want , but it 'd be great if you became a teacher . '' ( laughter ) but i wanted to be an entrepreneur , so i did n't . but it has always been my dream to actually teach something . so i said , `` what if i just ask and teach a college class ? '' i lived in austin at the time , so i went to university of texas at austin and knocked on professors ' doors and said , `` can i teach your class ? '' i did n't get anywhere the first couple of times . but because i did n't run -- i kept doing it -- and on the third try the professor was very impressed . he was like , `` no one has done this before . '' and i came in prepared with powerpoints and my lesson . he said , `` wow , i can use this . why do n't you come back in two months ? i 'll fit you in my curriculum . '' and two months later i was teaching a class . this is me -- you probably ca n't see , this is a bad picture . you know , sometimes you get rejected by lighting , you know ? ( laughter ) but wow -- when i finished teaching that class , i walked out crying , because i thought i could fulfill my life dream just by simply asking . i used to think i have to accomplish all these things -- have to be a great entrepreneur , or get a phd to teach -- but no , i just asked , and i could teach . and in that picture , which you ca n't see , i quoted martin luther king , jr. why ? because in my research i found that people who really change the world , who change the way we live and the way we think , are the people who were met with initial and often violent rejections . people like martin luther king , jr. , like mahatma gandhi , nelson mandela , or even jesus christ . these people did not let rejection define them . they let their own reaction after rejection define themselves . and they embraced rejection . and we do n't have to be those people to learn about rejection , and in my case , rejection was my curse , was my boogeyman . it has bothered me my whole life because i was running away from it . then i started embracing it . i turned that into the biggest gift in my life . i started teaching people how to turn rejections into opportunities . i use my blog , i use my talk , i use the book i just published , and i 'm even building technology to help people overcome their fear of rejection . when you get rejected in life , when you are facing the next obstacle or next failure , consider the possibilities . do n't run . if you just embrace them , they might become your gifts as well . thank you . ( applause )

and here it is -- ( laughter ) you do n't have to read this through -- ( laughter ) this is also bad handwriting , but i did highlight some key words . you get the idea . ( laughter ) so ... that was another version of me : one who will conquer the world .

list some of the things that jia did to get purposely rejected .

as a wildfire rages through the grasslands , three lions and three wildebeest flee for their lives . to escape the inferno , they must cross over to the left bank of a crocodile-infested river . fortunately , there happens to be a raft nearby . it can carry up to two animals at a time , and needs as least one lion or wildebeest on board to row it across the river . there 's just one problem . if the lions ever outnumber the wildebeest on either side of the river , even for a moment , their instincts will kick in , and the results wo n't be pretty . that includes the animals in the boat when it 's on a given side of the river . what 's the fastest way for all six animals to get across without the lions stopping for dinner ? pause here if you want to figure it out for yourself . answer in : 3 answer in : 2 answer in : 1 if you feel stuck on a problem like this , try listing all the decisions you can make at each point , and the consequences each choice leads to . for instance , there are five options for who goes across first : one wildebeest , one lion , two wildebeest , two lions , or one of each . if one animal goes alone , it 'll just have to come straight back . and if two wildebeest cross first , the remaining one will immediately get eaten . so those options are all out . sending two lions , or one of each animal , can actually both lead to solutions in the same number of moves . for the sake of time , we 'll focus on the second one . one of each animal crosses . now , if the wildebeest stays and the lion returns , there will be three lions on the right bank . bad news for the two remaining wildebeest . so we need to have the lion stay on the left bank and the wildebeest go back to the right . now we have the same five options , but with one lion already on the left bank . if two wildebeest go , the one that stays will get eaten , and if one of each animal goes , the wildebeest on the raft will be outnumbered as soon as it reaches the other side . so that 's a dead end , which means that at the third crossing , only the two lions can go . one gets dropped off , leaving two lions on the left bank . the third lion takes the raft back to the right bank where the wildebeest are waiting . what now ? well , since we 've got two lions waiting on the left bank , the only option is for two wildebeest to cross . next , there 's no sense in two wildebeest going back , since that just reverses the last step . and if two lions go back , they 'll outnumber the wildebeest on the right bank . so one lion and one wildebeest take the raft back leaving us with one of each animal on the left bank and two of each on the right . again , there 's no point in sending the lion-wildebeest pair back , so the next trip should be either a pair of lions or a pair of wildebeest . if the lions go , they 'd eat the wildebeest on the left , so they stay , and the two wildebeest cross instead . now we 're quite close because the wildebeest are all where they need to be with safety in numbers . all that 's left is for that one lion to raft back and bring his fellow lions over one by one . that makes eleven trips total , the smallest number needed to get everyone across safely . the solution that involves sending both lions on the first step works similarly , and also takes eleven crossings . the six animals escape unharmed from the fire just in time and begin their new lives across the river . of course , now that the danger 's passed , it remains to be seen how long their unlikely alliance will last .

one gets dropped off , leaving two lions on the left bank . the third lion takes the raft back to the right bank where the wildebeest are waiting . what now ?

after the wildebeest rafts back ( second crossing ) , which animal ( s ) now raft from the right side of the river to the left side ( third crossing ) ?

ralph waldo emerson is the father of american literature . in a series of strikingly original essays , written in the mid-nineteenth century , he fundamentally changed the way that america saw its cultural and artistic possibilities , and he enabled a separation from transatlantic literary traditions . `` we have listened too long ... '' , he wrote , `` ... to the courtly muses of europe . '' emerson 's abjection of cultural traditions brought about what one contemporary called : `` america 's intellectual declaration of independence . '' and he established generational conflict and transformation as commanding ideas in american literature . emerson himself hardly seemed destined to fit a revolutionary mold . he was born in 1803 , the son of a boston preacher , and was descended from a line of new england ministers that went back to the bedrock of seventeenth-century puritanism . when his father died in 1811 , his mother took in boarders to pay the rent . still , she sent her son to harvard in 1817 , and then harvard divinity school to train for the priesthood in 1825 . as a young man , emerson was strongly influenced by a remarkable aunt of his : mary moody emerson , who though self-taught , had read everything from shakespeare to the romantics and it formed a unique religious perspective based on piety nature and literature , that would resonate powerfully in the life and work of her nephew . so when emerson was ordained in 1829 , marrying the love of his life ellen tucker in the same year , he was already unsatisfied with the formal nature of new england religious orthodoxy . when ellen died of tuberculosis just two years later , he resigned from the church and soon after embarked on a trip to europe . leaving on christmas day 1832 , two crucial things happened to emerson on that tour of europe . in paris , he went to the famous `` jardin des plantes '' , a botanical and zoological garden . there he had an epiphany . writing in his journal that : `` i feel the centipede in me , the cayman , carp , eagle and fox ... ... i am moved by strange sympathies . i say continually : i will be a naturalist . `` . emerson 's insight was that nature is in us , a part of us , and not just its higher forms , but in all its grotesquerie and wildness . the second thing that happened on that tour , was that emerson met the english romantic poets : samuel taylor coleridge and william wordsworth , and found them rather ordinary , dry and conservative men . the insight that emerson drew from this , was that if great men could be so ordinary , why should not ordinary men be great ? as he would write a few years later , meek young men grow up in libraries , believing it their duty , to accept the views which cicero , locke , bacon have given . forgetful that cicero , locke and bacon were only young men in libraries when they wrote these books . emerson had found two ideas that would guide his life 's work . that man and nature are one and that everyone can recognize that they are a uniquely , significant human being . on his return to america in 1833 , emerson became a professional lecturer giving talks on natural history and literature in halls around new england . he remarried and had several children , presenting a stolid , bourgeois appearance to the world . but his inner life was full of turbulence and originality . in his 1836 essay , `` nature '' , emerson outlined the germ of a new philosophy , a key element of this , was the importance of american originality . in its opening lines , emerson wrote : `` our age is retrospective , it builds the sepulchres of the fathers . it writes biographies , histories and criticism . the foregoing generations beheld god and nature face to face ; we , through their eyes . why should not we also enjoy an original relation to the universe ? `` . america , needed to stop looking back to its european heritage and start looking about it self . no past moment was more important , than the present moment . no tradition was more important , than novelty . no generation , was better than the current generation . everything that matters is here now insisted emerson , and that here was : america . this was an extension of emerson 's ideas , about the significance of the individual that came under the heading of what he called `` self-reliance '' . everywhere emerson looked , he saw people leading lives that were based on tradition , that were limited by religious forms and social habits . no one could be themselves , emerson thought , because they were all too busy being what they were supposed to be . emerson wanted to get rid of each of these burdens : the past , religion and social forms , so that each person could find out who they truly were . as he put it : `` history is an impertinence and an injury ; our religion , we have not chosen , but society has chosen for us ... and ... ... society everywhere is in conspiracy against the manhood of every one of its members . '' we must , he argued , live from within trusting nothing but our own intuitions . for , as he concluded ... ... nothing is at last sacred but the integrity of your own mind . this leaves open a vital question : what is your nature ... ... once you 've rid yourself of history , tradition and religion ? what can be said is that it is n't necessarily self-indulgence , haterism or narcissism . rather , it 's the surrender to that force which emerson recognized back in the jardin des plantes . an obedience to nature itself . by nature , emerson seem to mean the natural world : plants , animals , rocks and sky , but what he really meant was god . emerson was a `` pantheist '' . that is , someone who believe that god exists in every part of creation , from the smallest grain of sand to the stars . but also crucially that the divine spark is in each of us . in following ourselves , we are therefore not merely being fickle or selfish , we are rather , releasing a divine will , that history , society and organized religion normally hide from us . the individual as emerson writes `` is a god in ruins '' . but we have it within us , by casting off all custom to rebuild ourselves emerson makes this pantheist connection , explicit in what are perhaps his most famous lines . `` crossing a bear common , in snow puddles at twilight under a clouded sky , without having in my thoughts any occurrence of special good fortune , i 've enjoyed a perfect exhilaration . i am glad to the brink of fear , standing on the bare ground , my head bathed by the blythe air and uplifted into infinite space , all mean egotism vanishes ... ... i become a transparent eyeball ... ... i am nothing ... ... i see all . the currents of the universal being circulate through me ... ... i am part or particle of god ! in the romantic tradition on which emerson draws , it is the sublime , great mountains , rushing torrance , dark forests , which releases the inner vision as we find ourselves in all of them . for emerson , it 's a perfectly dull walk across an ordinary common on a dark winter 's evening that brings him , to the brink of fear . emerson 's god , is in the snow puddles too . stood there on the common , he disappears , becoming nothing as the currents of god flow through him . what is left is just , a transparent eyeball . such transcendent moments are rare , but they reveal an essential connection between nature , god and man . they are one . they also give emerson a proper sense of each individual 's importance , as a part of god . transcendentalism became the name of the movement that grew up around emerson , at this time . another aspect of the epiphany that was to have a profound effect on american literature , was the emphasis on the value of the ordinary . what emerson put forward in essays like `` the american scholar '' and `` the poet '' , was that the american every day , was a proper subject for literature . this was because for emerson , the transcendentalist god is everywhere , and it 's the poet 's job to reveal this . `` there is no object ... '' , he wrote , `` ... so foul that intense light will not make it beautiful . '' `` ... even a corpse has its own beauty . '' this coming from a man who had opened his first wife 's tomb a year after her death ... ... to take a look ! the great american writers , who followed emerson , were liberated by his work to look around and write about what they saw and how they lived , transforming the everyday into a vital symbol of something higher and more elusive . henry david thoreau 's two years at walden pond , became a book that showed the cosmos reflected in the depths of the waters of a mere pond . the poet walt whitman said : `` i was simmering , simmering , simmering ... ... emerson brought me to a boil . '' emily dickinson heard a fly and could write of the other side of death . the novelist herman melville , took a whaling voyage , and made it an allegory of american imperialism and the defiance of nature . in the 20th century , the american critic harold bloom looked back at emerson 's originality and saw in it the origin of : `` the strong tradition of american poets . '' from robert frost and wallace stevens to john ashbery , emerson 's legacy to american literature and culture and indeed to the world , was one of ceaseless invention and forward momentum . as he put it : `` i unsettle all things ... ... no facts are to me sacred , none are profane ... ... i simply experiment an endless seeker with no past at my back . '' people of paul pronouncing his name if you do n't speak german it 's not at all obvious how you 're supposed to say it a safe bet is to start with a hard was a great check writer who has come to own a part of the human emotional spectrum which we can now call the casket desk and which thanks to him where

everywhere emerson looked , he saw people leading lives that were based on tradition , that were limited by religious forms and social habits . no one could be themselves , emerson thought , because they were all too busy being what they were supposed to be . emerson wanted to get rid of each of these burdens : the past , religion and social forms , so that each person could find out who they truly were . as he put it : `` history is an impertinence and an injury ; our religion , we have not chosen , but society has chosen for us ... and ... ... society everywhere is in conspiracy against the manhood of every one of its members . ''

emerson was a transcendentalist . a chief tenant of his belief system was that by transcending the influence of society and becoming completely self-reliant , a person could ...

tattoos have often been presented in popular media as either marks of the dangerous and deviant or trendy youth fads . but while tattoo styles come and go , and their meaning has differed greatly across cultures , the practice is as old as civilization itself . decorative skin markings have been discovered in human remains all over the world , with the oldest found on a peruvian mummy dating back to 6,000 bce . but have you ever wondered how tattooing really works ? you may know that we shed our skin , losing about 30-40,000 skin cells per hour . that 's about 1,000,000 per day . so , how come the tattoo does n't gradually flake off along with them ? the simple answer is that tattooing involves getting pigment deeper into the skin than the outermost layer that gets shed . throughout history , different cultures have used various methods to accomplish this . but the first modern tattooing machine was modeled after thomas edison 's engraving machine and ran on electricity . tattooing machines used today insert tiny needles , loaded with dye , into the skin at a frequency of 50 to 3,000 times per minute . the needles punch through the epidermis , allowing ink to seep deep into the dermis , which is composed of collagen fibers , nerves , glands , blood vessels and more . every time a needle penetrates , it causes a wound that alerts the body to begin the inflammatory process , calling immune system cells to the wound site to begin repairing the skin . and it is this very process that makes tattoos permanent . first , specialized cells called macrophages eat the invading material in an attempt to clean up the inflammatory mess . as these cells travel through the lymphatic system , some of them are carried back with a belly full of dye into the lymph nodes while others remain in the dermis . with no way to dispose of the pigment , the dyes inside them remain visible through the skin . some of the ink particles are also suspended in the gel-like matrix of the dermis , while others are engulfed by dermal cells called fibroblasts . initially , ink is deposited into the epidermis as well , but as the skin heals , the damaged epidermal cells are shed and replaced by new , dye-free cells with the topmost layer peeling off like a heeling sunburn . blistering or crusting is not typically seen with professional tattoos and complete epidermal regeneration requires 2-4 weeks , during which excess sun exposure and swimming should be avoided to prevent fading . dermal cells , however , remain in place until they die . when they do , they are taken up , ink and all , by younger cells nearby , so the ink stays where it is . but with time , tattoos do fade naturally as the body reacts to the alien pigment particles , slowly breaking them down to be carried off by the immune system 's macrophages . ultraviolet radiation can also contribute to this pigment breakdown , though it can be mitigated by the use of sunblock . but since the dermal cells are relatively stable , much of the ink will remain deep in the skin for a person 's whole life . but if tattoos are embedded in your skin for life , is there any way to erase them ? technically , yes . today , a laser is used to penetrate the epidermis and blast apart underlying pigment colors of various wavelengths , black being the easiest to target . the laser beam breaks the ink globules into smaller particles that can then be cleared away by the macrophages . but some color inks are harder to remove than others , and there could be complications . for this reason , removing a tattoo is still more difficult than getting one , but not impossible . so a single tattoo may not truly last forever , but tattoos have been around longer than any existing culture . and their continuing popularity means that the art of tattooing is here to stay .

the needles punch through the epidermis , allowing ink to seep deep into the dermis , which is composed of collagen fibers , nerves , glands , blood vessels and more . every time a needle penetrates , it causes a wound that alerts the body to begin the inflammatory process , calling immune system cells to the wound site to begin repairing the skin . and it is this very process that makes tattoos permanent .

every time the needle penetrates the skin , it causes the wound to initiate which bodily process ?

when a team of archaeologists recently came across some 15,000 year-old human remains , they made an interesting discovery . the teeth of those ancient humans were riddled with holes . their cavities were caused by the same thing that still plagues us today , specific tiny microbes that live in our mouths . these microbes are with us soon after birth . we typically pick them up as babies from our mothers ' mouths . and as our teeth erupt , they naturally begin to accumulate communities of bacteria . depending on what we eat , and specifically how much sugar we consume , certain microbes can overpopulate and cause cavities . diets high in sugary foods cause an explosion of bacteria called mutans streptococci in our mouths . like humans , these microorganisms love sugar , using it as a molecular building block and energy source . as they consume it , the bacteria generate byproducts in the form of acids , such as lactic acid . mutans streptococci are resistant to this acid , but unfortunately , our teeth are n't . while each human tooth is coated in a hardy , protective layer of enamel , it 's no match for acid . that degrades the armor over time , leaching away its calcium minerals . gradually , acid wears down a pathway for bacteria into the tooth 's secondary layer called the dentin . since blood vessels and nerves in our teeth are enclosed deep within , at this stage , the expanding cavity does n't hurt . but if the damage extends beyond the dentin , the bacterial invasion progresses causing excruciating pain as the nerves become exposed . without treatment , the whole tooth may become infected and require removal all due to those sugar-loving bacteria . the more sugar our food contains , the more our teeth are put at risk . those cavemen would hardly have indulged in sugary treats , however , so what caused their cavities ? in meat-heavy diets , there would have been a low-risk of cavities developing because lean meat contains very little sugar , but that 's not all our early human ancestors ate . cavemen would also have consumed root vegetables , nuts , and grains , all of which contain carbohydrates . when exposed to enzymes in the saliva , carbohydrates get broken down into simpler sugars , which can become the fodder for those ravenous mouth bacteria . so while ancient humans did eat less sugar compared to us , their teeth were still exposed to sugars . that does n't mean they were unable to treat their cavities , though . archaeological remains show that about 14,000 years ago , humans were already using sharpened flint to remove bits of rotten teeth . ancient humans even made rudimentary drills to smooth out the rough holes left behind and beeswax to plug cavities , like modern-day fillings . today , we have much more sophisticated techniques and tools , which is fortunate because we also need to contend with our more damaging , sugar-guzzling ways . after the industrial revolution , the human incidence of cavities surged because suddenly we had technological advances that made refined sugar cheaper and accessible . today , an incredible 92 % of american adults have had cavities in their teeth . some people are more susceptible to cavities due to genes that may cause certain weaknesses , like softer enamel , but for most , high sugar consumption is to blame . however , we have developed other ways of minimizing cavities besides reducing our intake of sugar and starch . in most toothpastes and many water supplies , we use tiny amounts of fluoride . that strengthens teeth and encourages the growth of enamel crystals that build up a tooth 's defenses against acid . when cavities do develop , we use tooth fillings to fill and close off the infected area , preventing them from getting worse . the best way to avoid a cavity is still cutting down on sugar intake and practicing good oral hygiene to get rid of the bacteria and their food sources . that includes regular tooth brushing , flossing , and avoiding sugary , starchy , and sticky foods that cling to your teeth between meals . gradually , the population of sugar-loving microbes in your mouth will decline . unlike the cavemen of yesteryear , today we have the knowledge required to avert a cavity calamity . we just need to use it .

we typically pick them up as babies from our mothers ' mouths . and as our teeth erupt , they naturally begin to accumulate communities of bacteria . depending on what we eat , and specifically how much sugar we consume , certain microbes can overpopulate and cause cavities .

bacteria ruin our teeth by producing :

one foggy morning in 1884 , the british steamer `` rumney '' crashed into the french ship `` frigorifique . '' seeing their ship filling with water , the french crew climbed aboard the `` rumney . '' but as they sailed towards the nearest port , a silent form suddenly emerged from the fog : the abandoned `` frigorifique . '' it was too late to turn , and the impact was enough to sink the `` rumney . '' as the sailors scrambled into the lifeboats , the empty `` frigorifique '' sailed back into the fog , having seemingly taken its revenge . in reality , the french sailors had left the engines running , and the `` frigorifique '' sailed in a circle before striking the `` rumney '' and finally sinking . but its story became one of the many tales of ghost ships , unmanned vessels that apparently sail themselves . and although they 've influenced works like `` dracula '' and `` pirates of the caribbean , '' crewless ships are n't the product of ghostly spirits , just physics at work . one of the most famous ghost ships was the `` mary celeste '' found sailing the atlantic in 1872 with no one aboard , water in its hold , and lifeboats missing . the discovery of its intact cargo and a captain 's log that ended abruptly led to wild rumors and speculation . but the real culprits were two scientific phenomena : buoyancy and fluid dynamics . here 's how buoyancy works . an object placed in a liquid displaces a certain volume of fluid . the liquid in turn exerts an upward buoyant force equal to the weight of the fluid that 's been displaced . this phenomenon is called archimedes 's principle . objects that are less dense than water , such as balsa wood , icebergs , and inflatable rafts always float . that 's because the upward buoyant force is always stronger than the downward force of gravity . but for objects or ships to float when they 're made of materials , like steel , that are denser than water , they must displace a volume of water larger than their weight . normally , the water filling a ship 's hull would increase its weight and cause it to sink - just what the `` mary celeste 's '' crew feared when they abandoned ship . but the sailors did n't account for fluid dynamics . the water stopped flowing at the point of equilibrium , when it reached the same level as the hull . as it turned out , the weight of the water was n't enough to sink the ship and the `` mary celeste '' was found a few days later while the unfortunate crew never made it to shore . far stranger is the tale of `` a. ernest mills , '' a schooner transporting salt , whose crew watched it sink to the sea floor following a collision . yet four days later , it was spotted floating on the surface . the key to the mystery lay in the ship 's heavy cargo of salt . the added weight of the water in the hull made the vessel sink , but as the salt dissolved in the water , the weight decreased enough that the force of gravity became less than the buoyant force and the ship floated back to the surface . but how do we explain the most enduring aspect of ghost ship legends : multiple sightings of the same ships hundreds of miles and several years apart ? the answer lies in ocean currents , which are like invisible rivers flowing through the ocean . factors , like temperature , salinity , wind , gravity , and the coriolis effect from the earth 's rotation create a complex system of water movement . that applies both at the ocean 's surface and deep below . sailors have always known about currents , but their patterns were n't well known until recently . in fact , tracking abandoned ships was how scientists determined the shape and speed of the atlantic gyre , the gulf stream , and related currents in the first place . beginning in 1883 , the u.s. hydrographic office began collecting monthly data that included navigation hazards , like derelict ships , whose locations were reported by passing vessels . so abandoned ships may not be moved by ghost crews or supernatural curses , but they are a real and fascinating phenomenon born through the ocean and kept afloat by powerful , invisible , scientifically studied forces .

but for objects or ships to float when they 're made of materials , like steel , that are denser than water , they must displace a volume of water larger than their weight . normally , the water filling a ship 's hull would increase its weight and cause it to sink - just what the `` mary celeste 's '' crew feared when they abandoned ship . but the sailors did n't account for fluid dynamics .

the `` mary celeste '' became a ghost ship due to :

before he turned physics upside down , a young albert einstein supposedly showed off his genius by devising a complex riddle involving this list of clues . can you resist tackling a brain teaser written by one of the smartest people in history ? let 's give it a shot . the world 's rarest fish has been stolen from the city aquarium . the police have followed the scent to a street with five identical looking houses . but they ca n't search all the houses at once , and if they pick the wrong one , the thief will know they 're on his trail . it 's up to you , the city 's best detective , to solve the case . when you arrive on the scene , the police tell you what they know . one : each house 's owner is of a different nationality , drinks a different beverage , and smokes a different type of cigar . two : each house 's interior walls are painted a different color . three : each house contains a different animal , one of which is the fish . after a few hours of expert sleuthing , you gather some clues . it may look like a lot of information , but there 's a clear logical path to the solution . solving the puzzle will be a lot like sudoku , so you may find it helpful to organize your information in a grid , like this . pause the video on the following screen to examine your clues and solve the riddle . answer in : 3 2 1 to start , you fill in the information from clues eight and nine . immediately , you also realize that since the norwegian is at the end of the street , there 's only one house next to him , which must be the one with the blue walls in clue fourteen . clue five says the green-walled house 's owner drinks coffee . it ca n't be the center house since you already know its owner drinks milk , but it also ca n't be the second house , which you know has blue walls . and since clue four says the green-walled house must be directly to the left of the white-walled one , it ca n't be the first or fifth house either . the only place left for the green-walled house with the coffee drinker is the fourth spot , meaning the white-walled house is the fifth . clue one gives you a nationality and a color . since the only column missing both these values is the center one , this must be the brit 's red-walled home . now that the only unassigned wall color is yellow , this must be applied to the first house , where clue seven says the dunhill smoker lives . and clue eleven tells you that the owner of the horse is next door , which can only be the second house . the next step is to figure out what the norwegian in the first house drinks . it ca n't be tea , clue three tells you that 's the dane . as per clue twelve , it ca n't be root beer since that person smokes bluemaster , and since you already assigned milk and coffee , it must be water . from clue fifteen , you know that the norwegian 's neighbor , who can only be in the second house , smokes blends . now that the only spot in the grid without a cigar and a drink is in the fifth column , that must be the home of the person in clue twelve . and since this leaves only the second house without a drink , the tea-drinking dane must live there . the fourth house is now the only one missing a nationality and a cigar brand , so the prince-smoking german from clue thirteen must live there . through elimination , you can conclude that the brit smokes pall mall and the swede lives in the fifth house , while clue six and clue two tell you that these two have a bird and a dog , respectively . clue ten tells you that the cat owner lives next to the blend-smoking dane , putting him in the first house . now with only one spot left on the grid , you know that the german in the green-walled house must be the culprit . you and the police burst into the house , catching the thief fish-handed . while that explanation was straightforward , solving puzzles like this often involves false starts and dead ends . part of the trick is to use the process of elimination and lots of trial and error to hone in on the right pieces , and the more logic puzzles you solve , the better your intuition will be for when and where there 's enough information to make your deductions . and did young einstein really write this puzzle ? probably not . there 's no evidence he did , and some of the brands mentioned are too recent . but the logic here is not so different from what you 'd use to solve equations with multiple variables , even those describing the nature of the universe .

the next step is to figure out what the norwegian in the first house drinks . it ca n't be tea , clue three tells you that 's the dane . as per clue twelve , it ca n't be root beer since that person smokes bluemaster , and since you already assigned milk and coffee , it must be water .

which of the following pieces did not aid in determining that the dane owns a horse ?

in the early 1960s , dick fosbury tried his hand at almost every sport , but never excelled at anything , until , at the age of 16 , he turned to the high jump . but when he could n't compete against the strong athletes at his college using the standard high jump techniques of the time , fosbury tried to jump a different way : backwards . instead of jumping with his face towards the bar , bringing each leg over in the traditional straddle method , he jumped with his back towards the bar . fosbury improved his record by over half a foot , and left his coaches amazed by this strange new style of high jumping . during the next few years , fosbury perfected his high jump style , won the u.s. national trials , and assured his place in the 1968 olympics in mexico . in the olympic games , fosbury amazed the world with his new technique , winning a gold metal with an olympic record leap of 2.24 meters . by the next olympic games , almost all of the competing of high jumpers had adopted what came to be known as the fosbury flop . what 's the secret behind the technique ? it lies in a physics concept called the center of mass . for every object , we can locate the average position of all of its mass by taking into account how the mass is spread around the object . for instance , the center of mass of a flat , rectangular object of uniform density will be in the intersection of both diagonals , in equal distance from each corner . we can find the center of mass for other objects by similar calculations , or by finding the object 's balancing point , which lies right underneath its center of mass . try balancing a broom by holding it and slowly bringing your hands together until they meet . this balancing point lies right underneath the broom 's center of mass . we humans also have a center of mass . when most people stand up , their center of mass is around the belly , but what happens to your center of mass when you lift your hands in the air ? your center of mass moves upwards . it moves all the time as you move through the day , based on how your body is positioned . it can even move outside of your body . when you bend forward , your center of mass is located below your bent belly in a place where there is no mass at all . weird to think about , but that 's the average position of all your mass . many objects ' center of mass are outside their bodies . think of doughnuts or boomerangs . now look at the fosbury flop , and follow the position of the center of mass of the jumper . the jumper runs very fast , so he can divert his horizontal velocity to vertical velocity , and jumps . wait for it ... there . look at the jumper 's center of mass as his body bends backward . it 's below the bar . that is the secret behind the jump . with the old , pre-fosbury techniques , the jumper had to apply enough force to lift his center of mass above the bar by a few inches in order to clear it . the fosbury flopper does n't have to do that . the genius of the fosbury flop is that the jumper can apply the same amount of force , but raise his body much higher than before . that means he can raise the bar so high that even when his center of mass ca n't go any higher , his arching body can . fosbury 's technique brought the high jump to new heights by splitting the jumper 's body away from his center of mass , giving it that much more room to clear higher and higher bars . so the fosbury flop may be sports history 's only great leap forward , that is also a great leap backward .

in the olympic games , fosbury amazed the world with his new technique , winning a gold metal with an olympic record leap of 2.24 meters . by the next olympic games , almost all of the competing of high jumpers had adopted what came to be known as the fosbury flop . what 's the secret behind the technique ?

why do you think high jumpers need to be very flexible in order to succeed in jumping using the fosbury flop ?

hendrix , cobain and page . they can all shred , but how exactly do the iconic contraptions in their hands produce notes , rhythm , melody and music . when you pluck a guitar string , you create a vibration called a standing wave . some points on the string , called nodes , do n't move at all , while other points , anti-nodes , oscillate back and forth . the vibration translates through the neck and bridge to the guitar 's body , where the thin and flexible wood vibrates , jostling the surrounding air molecules together and apart . these sequential compressions create sound waves , and the ones inside the guitar mostly escape through the hole . they eventually propagate to your ear , which translates them into electrical impulses that your brain interprets as sound . the pitch of that sound depends on the frequency of the compressions . a quickly vibrating string will cause a lot of compressions close together , making a high-pitched sound , and a slow vibration produces a low-pitched sound . four things affect the frequency of a vibrating string : the length , the tension , the density and the thickness . typical guitar strings are all the same length , and have similar tension , but vary in thickness and density . thicker strings vibrate more slowly , producing lower notes . each time you pluck a string , you actually create several standing waves . there 's the first fundamental wave , which determines the pitch of the note , but there are also waves called overtones , whose frequencies are multiples of the first one . all these standing waves combine to form a complex wave with a rich sound . changing the way you pluck the string affects which overtones you get . if you pluck it near the middle , you get mainly the fundamental and the odd multiple overtones , which have anti-nodes in the middle of the string . if you pluck it near the bridge , you get mainly even multiple overtones and a twangier sound . the familiar western scale is based on the overtone series of a vibrating string . when we hear one note played with another that has exactly twice its frequency , its first overtone , they sound so harmonious that we assign them the same letter , and define the difference between them as an octave . the rest of the scale is squeezed into that octave divided into twelve half steps whose frequency is each 2^ ( 1/12 ) higher than the one before . that factor determines the fret spacing . each fret divides the string 's remaining length by 2^ ( 1/12 ) , making the frequencies increase by half steps . fretless instruments , like violins , make it easier to produce the infinite frequencies between each note , but add to the challenge of playing intune . the number of strings and their tuning are custom tailored to the chords we like to play and the physiology of our hands . guitar shapes and materials can also vary , and both change the nature and sound of the vibrations . playing two or more strings at the same time allows you to create new wave patterns like chords and other sound effects . for example , when you play two notes whose frequencies are close together , they add together to create a sound wave whose amplitude rises and falls , producing a throbbing effect , which guitarists call the beats . and electric guitars give you even more to play with . the vibrations still start in the strings , but then they 're translated into electrical signals by pickups and transmitted to speakers that create the sound waves . between the pickups and speakers , it 's possible to process the wave in various ways , to create effects like distortion , overdrive , wah-wah , delay and flanger . and lest you think that the physics of music is only useful for entertainment , consider this . some physicists think that everything in the universe is created by the harmonic series of very tiny , very tense strings . so might our entire reality be the extended solo of some cosmic jimi hendrix ? clearly , there 's a lot more to strings than meets the ear .

the familiar western scale is based on the overtone series of a vibrating string . when we hear one note played with another that has exactly twice its frequency , its first overtone , they sound so harmonious that we assign them the same letter , and define the difference between them as an octave . the rest of the scale is squeezed into that octave divided into twelve half steps whose frequency is each 2^ ( 1/12 ) higher than the one before .

if you double the frequency of a particular note on any instrument you get a ( n ) :

what makes a book a book ? is it just anything that stores and communicates information ? or does it have to do with paper , binding , font , ink , its weight in your hands , the smell of the pages ? is this a book ? probably not . but is this ? to answer these questions , we need to go back to the start of the book as we know it and understand how these elements came together to make something more than the sum of their parts . the earliest object that we think of as a book is the codex , a stack of pages bound along one edge . but the real turning point in book history was johannes gutenberg 's printing press in the mid-15th century . the concept of moveable type had been invented much earlier in eastern culture , but the introduction of gutenberg 's press had a profound effect . suddenly , an elite class of monks and the ruling class no longer controlled the production of texts . messages could spread more easily , and copies could constantly be produced , so printing houses popped up all over europe . the product of this bibliographic boom is familiar to us in some respects , but markedly different in others . the skeleton of the book is paper , type , and cover . more than 2000 years ago , china invented paper as a writing surface , which was itself predated by egyptian papyrus . however , until the 16th century , europeans mainly wrote on thin sheets of wood and durable parchment made of stretched animal skins . eventually , the popularity of paper spread throughout europe , replacing parchment for most printings because it was less expensive in bulk . inks had been made by combining organic plant and animal dyes with water or wine , but since water does n't stick to metal type , use of the printing press required a change to oil-based ink . printers used black ink made of a mixture of lamp soot , turpentine , and walnut oil . and what about font size and type ? the earliest movable type pieces consisted of reversed letters cast in relief on the ends of lead alloy stocks . they were handmade and expensive , and the designs were as different as the people who carved their molds . standardization was not really possible until mass manufacturing and the creation of an accessible word processing system . as for style , we can thank nicolas jenson for developing two types of roman font that led to thousands of others , including the familiar times roman . something had to hold all this together , and until the late 15th century , covers consisted of either wood , or sheets of paper pasted together . these would eventually be replaced by rope fiber millboard , originally intended for high quality bindings in the late 17th century , but later as a less expensive option . and while today 's mass produced cover illustrations are marketing tools , the cover designs of early books were made to order . even spines have a history . initially , they were not considered aesthetically important , and the earliest ones were flat , rather than rounded . the flat form made the books easier to read by allowing the book to rest easily on a table . but those spines were damaged easily from the stresses of normal use . a rounded form solved that issue , although new problems arose , like having the book close in on itself . but flexibility was more important , especially for the on-the-go reader . as the book evolves and we replace bound texts with flat screens and electronic ink , are these objects and files really books ? does the feel of the cover or the smell of the paper add something crucial to the experience ? or does the magic live only within the words , no matter what their presentation ?

eventually , the popularity of paper spread throughout europe , replacing parchment for most printings because it was less expensive in bulk . inks had been made by combining organic plant and animal dyes with water or wine , but since water does n't stick to metal type , use of the printing press required a change to oil-based ink . printers used black ink made of a mixture of lamp soot , turpentine , and walnut oil .

once the printing press existed , would water-based ink work in the printing process ?

remember the time you fell off your bike or bumped your head on a sharp corner ? childhood injuries are things we 'd often like to forget , but our bodies often carry the memories in the form of scars . so what are these unwanted souvenirs and why do we keep them for so long after that unintended vacation to the emergency room ? the most common place we see scars are on our skin , a patch that looks slightly different from the normal skin around it . often , this is considered an unfortunate disfigurement , while other times , deliberate scarification has been used in both traditional and modern cultures , to mark a rite of passage or simply for aesthetic decoration . but the difference is n't only cosmetic . when we look at healthy skin tissue under a microscope , we see the cells that perform various functions connected by an extracellular matrix , or ecm . this is composed of structural proteins , like collagen , secreted by specialized fibroblast cells . well-arranged ecm allows for transportation of nutrients , cell-to-cell communication , and cell adhesion . but when a deep wound occurs , this arrangement is disrupted . during the process of wound healing , collagen is redeposited at the wound site , but instead of the basket-weave formation found in healthy tissue , the new ecm is aligned in a single direction , impeding inter-cell processes , and reducing durability and elasticity . to make matters worse , the healed tissue contains a higher proportion of ecm than before , reducing its overall function . in the skin , the overabundance of collagen interferes with its original functions , like producing sweat , controlling body temperature and even growing hair . the scar tissue is fragile , sensitive to changes in temperature and sensation , and should be kept in moist environments to maximize healing . this presence of excessive fibrous connective tissue in an organ is known as fibrosis , and if that term sounds familiar , it 's because our skin is not the only organ vulnerable to scarring . cystic fibrosis is a genetic disorder that causes scarring of the pancreas , while pulmonary fibrosis is a scarring of the lungs , resulting in shortness of breath . scarring of the heart and the buildup of ecm following a heart attack can inhibit its beating , leading to further heart problems . what 's common to all these conditions is that although it retains some of the original functions , the scar tissue formed after a wound is inferior to the native tissue it replaces . however , there is hope . medical researchers are now studying what causes fibroblast cells to secrete excessive amounts of collagen and how we can recruit the body 's other cells in regenerating and repopulating the damaged tissue . by learning how to better control wound healing and the formation of scar tissue , we can utilize the multi-billion-dollar budgets currently used to address the aftermath of wounding in a much more efficient manner , and help millions of people live better and healthier lives . but until then , at least some of our scars can help us remember to avoid the sorts of things that cause them .

so what are these unwanted souvenirs and why do we keep them for so long after that unintended vacation to the emergency room ? the most common place we see scars are on our skin , a patch that looks slightly different from the normal skin around it . often , this is considered an unfortunate disfigurement , while other times , deliberate scarification has been used in both traditional and modern cultures , to mark a rite of passage or simply for aesthetic decoration .

human branding , a process in which a pattern is burnt onto the skin resulting in the formation of a scar , is practiced by different cultures to mark commemorative events through scaring . what could be the potential risks associated with these traditions ?

you might think you know a lot about native americans through popular movies , books , and classes in school , but it turns out that a lot of what we think we know about famous native american figures is n't quite right . take sacajawea for example . you probably remember her as a beautiful indian woman who lived an exotic life serving as the all-knowing guide for lewis and clark 's famous expedition , right ? well , that 's not exactly how it happened . not much is known about sacajawea 's early childhood , but we do know that she was born in 1788 into the agaidika tribe of the lemhi shoshone in what is now idaho . in 1800 , when she was about 12 years old , sacajawea and several other girls were kidnapped by a group of hidatsa indians . she was taken as a captive to a hidatsa village in present-day north dakota . then , she was sold to a french canadian fur trapper named toussaint charbonneau . within a year or so , she was pregnant with her first child . soon after she became pregnant , the corps of discovery arrived near the hidatsa villages . captains meriwether lewis and william clark built fort mandan there , and then started interviewing people to help guide them on their perilous expedition . they agreed to hire sacajawea 's husband , charbonneau , with the understanding that his lovely wife would also come along as an interpreter . they figured her very presence would help any encounters with native tribes along the way . as clark noted in his journal , `` a woman with a party of men is a token of peace . '' shortly thereafter , sacajawea gave birth to a little boy named jean baptiste charbonneau . clark called him pompy . she carried pompy on a board strapped to her back as the corps of discovery forged on . besides interpreting the language when lewis and clark encountered indians , sacajawea 's activities as a member of the corps included digging for roots , collecting edible plants , and picking berries . in 1805 , the boat they were riding in was capsized . she dove into the water , recovering all the important papers and supplies that would otherwise have been lost , including the journals and records of lewis and clark . later that year , captain lewis and three men scouted 75 miles ahead of the expedition 's main party , crossing the continental divide . the next day they encountered a group of shishones . not only did they prove to be sacajawea 's band , but their leader , chief cameahwait , turned out to be her very own brother . after five years of separation since her kidnapping as a young girl , sacajawea and cameahwait had an emotional reunion . unfortunately , she quickly had to bid farewell to her beloved brother and continue on with the journey . at one point , the expedition became so difficult and freezing , the group was reduced to eating candles to survive . when temperatures finally became more bearable , sacajawea found , dug , and cooked roots to help the group regain their strength . on the return trip , they encountered an indian wearing a beautiful fur robe . lewis and clark wanted to bring the robe to thomas jefferson as a gift but had nothing to trade for it . so , sacajawea agreed to trade her most precious possession , her beaded belt , for the fur . a little over two years after the expedition began , it was finally over , ending in st. louis . today , we learn about sacajawea in school as a heroic guide , but her life , like most everyone 's , was much more complicated than history books sometimes give her credit for .

unfortunately , she quickly had to bid farewell to her beloved brother and continue on with the journey . at one point , the expedition became so difficult and freezing , the group was reduced to eating candles to survive . when temperatures finally became more bearable , sacajawea found , dug , and cooked roots to help the group regain their strength .

at one point the expedition became so difficult and freezing , the group was reduced to eating ____________ to survive .

in the 18th century , swedish botanist carolus linnaeus designed the flower clock , a timepiece made of flowering plants that bloom and close at specific times of day . linnaeus 's plan was n't perfect , but the idea behind it was correct . flowers can indeed sense time , after a fashion . mornings glories unfurl their petals like clockwork in the early morning . a closing white water lily signals that it 's late afternoon , and moon flowers , as the name suggests , only bloom under the night sky . but what gives plants this innate sense of time ? it 's not just plants , in fact . many organisms on earth have a seemingly inherent awareness of where they are in the day 's cycle . that 's because of circadian rhythms , the internal timekeepers that tick away inside many living things . these biological clocks allow organisms to keep track of time and pick up on environmental cues that help them adapt . that 's important , because the planet 's rotations and revolutions put us in a state of constant flux , although it plays out in a repetitive , predictable way . circadian rhythms incorporate various cues to regulate when an organism should wake and sleep , and perform certain activities . for plants , light and temperature are the cues which trigger reactions that play out at a molecular scale . the cells in stems , leaves , and flowers contain phytochromes , tiny molecules that detect light . when that happens , phytochromes initiate a chain of chemical reactions , passing the message down into the cellular nuclei . there , transcription factors trigger the manufacture of proteins required to carry out light-dependent processes , like photosynthesis . these phytochromes not only sense the amount of light the plant receives , but can also detect tiny differences in the distribution of wavelengths the plant takes in . with this fine-tuned sensing , phytochromes allow the plant to discern both time , the difference between the middle of the day and the evening , and place , whether it is in direct sunlight or shade , enabling the plant to match its chemical reactions to its environment . this makes for early risers . a few hours before sunrise , a typical plant is already active , creating mrna templates for its photosynthesizing machinery . as the phytochromes detect increasing sunlight , the plant readies its light-capturing molecules so it can photosynthesize and grow throughout the morning . after harvesting their morning light , plants use the rest of the day to build long chains of energy in the form of glucose polymers , like starch . the sun sets , and the day 's work is done , though a plant is anything but inactive at night . in the absence of sunlight , they metabolize and grow , breaking down the starch from the previous day 's energy harvest . many plants have seasonal rhythms as well . as spring melts the winter frost , phytochromes sense the longer days and increasing light , and a currently unknown mechanism detects the temperature change . these systems pass the news throughout the plant and make it produce blooming flowers in preparation for the pollinators brought out by warmer weather . circadian rhythms act as a link between a plant and its environment . these oscillations come from the plants themselves . each one has a default rhythm . even so , these clocks can adapt their oscillations to environmental changes and cues . on a planet that 's in constant flux , it 's the circadian rhythms that enable a plant to stay true to its schedule and to keep its own time .

circadian rhythms incorporate various cues to regulate when an organism should wake and sleep , and perform certain activities . for plants , light and temperature are the cues which trigger reactions that play out at a molecular scale . the cells in stems , leaves , and flowers contain phytochromes , tiny molecules that detect light .

how do plants know the difference between morning light and afternoon light ?

so this a really beautiful sample of chromium . so chromium is a transition metal , right in the middle of the transition metals series there and it is used to protect metal components and very often you see chromium plated components on cars perhaps some of the older cars , you know , the wheel trims or perhaps the grills on the front , but if you look at the sample it is really lustrous , really beautiful and shiny . so there are some elements that one is really fond of and chromium is one of the metals that i really like . it is a metal you would have seen it in many places it is used for plating materials . this may actually be stainless steel but chromium looks very similar and it was very popular for plating bumpers , all sorts of materials in the 1930s up to the 1950s . so you can get dull chromium as well which is where the surface is very bumpy and the light tends to be absorbed a lot more and not reflected . my interest in chromium is that in the chemistry one of the very first bits of chemistry research i did in school was involving copper chromate . i spent months doing experiments on it . i did not really discover anything about it but it was great fun . at one stage i had a whole row of test tubes of copper chromate above my bed and my bedroom at home and more recently when i starting doing doctorates , i did experiments with chromium , making new complexes of chromium and one of the very first compounds that my research group ever made , that was new that nobody else had made before , was a compound of ethene and chromium - chromium pentacarbonyl ethene so i have very warm feelings about it .

so this a really beautiful sample of chromium . so chromium is a transition metal , right in the middle of the transition metals series there and it is used to protect metal components and very often you see chromium plated components on cars perhaps some of the older cars , you know , the wheel trims or perhaps the grills on the front , but if you look at the sample it is really lustrous , really beautiful and shiny . so there are some elements that one is really fond of and chromium is one of the metals that i really like .

which type of reaction is involved in the process that coats a piece of metal with chromium ( the process we know as “ chrome plating ” ) ?

translator : ido dekkers reviewer : ariana bleau lugo ( music ) the basic question is , does life exist beyond earth ? scientists who are called astrobiologists are trying to find that out right now . most astrobiologists are trying to figure out if there 's microbial life on mars , or in the ocean under the frozen surface of jupiter 's moon europa , or in the liquid hydrocarbon lakes that we 've found on saturn 's moon titan . but one group of astrobiologists works on seti . seti is the search for extraterrestrial intelligence , and seti researchers are trying to detect some evidence that intelligent creatures elsewhere have used technology to build a transmitter of some sort . but how likely is it that they will manage to find a signal ? there are certainly no guarantees when it comes to seti , but something called the drake equation , named after frank drake , can help us organize our thinking about what might be required for successful detection . if you 've dealt with equations before , then you probably expect that there will be a solution to the equation , a right answer . the drake equation , however , is different , because there are so many unknowns . it has no right answer . as we learn more about our universe and our place within it , some of the unknowns get better known , and we can estimate an answer a bit better . but there wo n't be a definite answer to the drake equation until seti succeeds or something else proves that earthlings are the only intelligent species in our portion of the cosmos . in the meantime , it is really useful to consider the unknowns . the drake equation attempts to estimate the number of technological civilizations in the milky way galaxy -- we call that n -- with whom we could make contact , and it 's usually written as : n equals r-star multiplied by f-sub-p multiplied by n-sub-e multiplied by f-sub-l multiplied by f-sub-i multiplied by f-sub-c and lastly , multiplied by capital l. all those factors multiplied together help to estimate the number of technological civilizations that we might be able to detect right now . r-star is the rate at which stars have been born in the milky way galaxy over the last few billion years , so it 's a number that is stars per year . our galaxy is 10 billion years old , and early in its history stars formed at a different rate . all of the f-factors are fractions . each one must be less than or equal to one . f-sub-p is the fraction of stars that have planets . n-sub-e is the average number of habitable planets in any planetary system . f-sub-l is the fraction of planets on which life actually begins and f-sub-i is the fraction of all those life forms that develop intelligence . f-sub-c is the fraction of intelligent life that develops a civilization that decides to use some sort of transmitting technology . and finally , l -- the longevity factor . on average , how many years do those transmitters continue to operate ? astronomers are now almost able to tell us what the product of the first three terms is . we 're now finding exoplanets almost everywhere . the fractions dealing with life and intelligence and technological civilizations are ones that many , many experts ponder , but nobody knows for sure . so far , we only know of one place in the universe where life exists , and that 's right here on earth . in the next couple of decades , as we explore mars and europa and titan , the discovery of any kind of life there will mean that life will be abundant in the milky way . because if life originated twice within this one solar system , it means it was easy , and given similar conditions elsewhere , life will happen . so the number two is a very important number here . scientists , including seti researchers , often tend to make very crude estimates and acknowledge that there are very large uncertainties in these estimates , in order to make progress . we think we know that r-star and n-sub-e are both numbers that are closer to 10 than , say , to one , and all the f-factors are less than one . some of them may be much less than one . but of all these unknowns , the biggest unknown is l , so perhaps the most useful version of the drake equation is simply to say that n is approximately equal to l. the information in this equation is very clear . unless l is large , n will be small . but , you know , you can also turn that around . if seti succeeds in detecting a signal in the near future , after examining only a small portion of the stars in the milky way , then we learn that l , on average , must be large . otherwise , we could n't have succeeded so easily . a physicist named philip morrison summarizes by saying that seti is the archaeology of the future . by this , he meant that because the speed of light is finite , any signals detected from distant technologies will be telling us about their past by the time they reach us . but because l must be large for a successful detection , we also learn about our future , particularly that we can have a long future . we 've developed technologies that can send signals into space and humans to the moon , but we 've also developed technologies that can destroy the environment , that can wage war with weapons and biological terrorism . in the future , will our technology help stabilize our planet and our population , leading to a very long lifetime for us ? or will we destroy our world and its inhabitants after only a brief appearance on the cosmic stage ? i encourage you to consider the unknowns in this equation . why do n't you make your own estimates for these unknowns , and see what you come up with for n ? compare that with the estimates made by frank drake , carl sagan , other scientists or your neighbors . remember , there 's no right answer . not yet .

in the next couple of decades , as we explore mars and europa and titan , the discovery of any kind of life there will mean that life will be abundant in the milky way . because if life originated twice within this one solar system , it means it was easy , and given similar conditions elsewhere , life will happen . so the number two is a very important number here .

take a moment to let your imagination go and think about the possibilities of technologically advanced alien life . what do you think that civilization would like and why ? do you think they would be at all similar to us ?

how do nerves work ? are nerves simply the wires in the body that conduct electricity , like the wires in the walls of your home or in your computer ? this is an analogy often made , but the reality is that nerves have a much more complex job in the body . they are not just the wires , but the cells that are the sensors , detectors of the external and internal world , the transducers that convert information to electrical impulses , the wires that transmit these impulses , the transistors that gate the information and turn up or down the volume- and finally , the activators that take that information and cause it to have an effect on other organs . consider this . your mother gently strokes your forearm and you react with pleasure . or a spider crawls on your forearm and you startle and slap it off . or you brush your forearm against a hot rack while removing a cake from the oven and you immediately recoil . light touch produced pleasure , fear , or pain . how can one kind of cell have so many functions ? nerves are in fact bundles of cells called neurons and each of these neurons is highly specialized to carry nerve impulses , their form of electricity , in response to only one kind of stimulus , and in only one direction . the nerve impulse starts with a receptor , a specialized part of each nerve , where the electrical impulse begins . one nerve 's receptor might be a thermal receptor , designed only to respond to a rapid increase in temperature . another receptor type is attached to the hairs of the forearm , detecting movement of those hairs , such as when a spider crawls on your skin . yet another kind of neuron is low-threshold mechanoreceptor , activated by light touch . each of these neurons then carry their specific information : pain , warning , pleasure . and that information is projected to specific areas of the brain and that is the electrical impulse . the inside of a nerve is a fluid that is very rich in the ion potassium . it is 20 times higher than in the fluid outside the nerve while that outside fluid has 10 times more sodium than the inside of a nerve . this imbalance between sodium outside and potassium inside the cell results in the inside of the nerve having a negative electrical charge relative to the outside of the nerve , about equal to -70 or -80 millivolts . this is called the nerve 's resting potential . but in response to that stimulus the nerve is designed to detect , pores in the cell wall near the receptor of the cell open . these pores are specialized protein channels that are designed to let sodium rush into the nerve . the sodium ions rush down their concentration gradient , and when they do , the inside of the nerve becomes more positively charged- about +40 millivolts . while this happens , initially in the nerve right around the receptor , if the change in the nerve 's electrical charge is great enough , if it reaches what is called threshold , the nearby sodium ion channels open , and then the ones nearby those , and so on , and so forth , so that the positivity spreads along the nerve 's membrane to the nerve 's cell body and then along the nerve 's long , thread-like extension , the axon . meanwhile , potassium ion channels open , potassium rushes out of the nerve , and the membrane voltage returns to normal . actually , overshooting it a bit . and during this overshoot , the nerve is resistant to further depolarization-it is refractory , which prevents the nerve electrical impulse from traveling backwards . then , ion pumps pump the sodium back back out of the nerve , and the potassium back into the nerve , restoring the nerve to its normal resting state . the end of the nerve , the end of the axon , communicates with the nerve 's target . this target will be other nerves in a specialized area of the spinal cord , to be processed and then transmitted up to the brain . or the nerve 's target may be another organ , such as a muscle . when the electrical impulse reaches the end of the nerve , small vesicles , or packets , containing chemical neurotransmitters , are released by the nerve and rapidly interact with the nerve 's target . this process is called synaptic transmission , because the connection between the nerve and the next object in the chain is called a synapse . and it is here , in this synapse , that the neuron 's electrical information can be modulated , amplified , blocked altogether or translated to another informational process .

or the nerve 's target may be another organ , such as a muscle . when the electrical impulse reaches the end of the nerve , small vesicles , or packets , containing chemical neurotransmitters , are released by the nerve and rapidly interact with the nerve 's target . this process is called synaptic transmission , because the connection between the nerve and the next object in the chain is called a synapse .

when the electrical impulse reaches the end of the nerve , small vesicles containing chemical neurotransmitters are released by the nerve and rapidly interact with the nerve ’ s target . this process is called :

consider the classic white t-shirt . annually , we sell and buy two billion t-shirts globally , making it one of the most common garments in the world . but how and where is the average t-shirt made , and what 's its environmental impact ? clothing items can vary a lot , but a typical t-shirt begins its life on a farm in america , china , or india where cotton seeds are sown , irrigated and grown for the fluffy bolls they produce . self-driving machines carefully harvest these puffs , an industrial cotton gin mechanically separates the fluffy bolls from the seeds , and the cotton lint is pressed into 225-kilogram bales . the cotton plants require a huge quantity of water and pesticides . 2,700 liters of water are needed to produce the average t-shirt , enough to fill more than 30 bathtubs . meanwhile , cotton uses more insecticides and pesticides than any other crop in the world . these pollutants can be carcinogenic , harm the health of field workers , and damage surrounding ecosystems . some t-shirts are made of organic cotton grown without pesticides and insecticides , but organic cotton makes up less than 1 % of the 22.7 million metric tons of cotton produced worldwide . once the cotton bales leave the farm , textile mills ship them to a spinning facility , usually in china or india , where high-tech machines blend , card , comb , pull , stretch , and , finally , twist the cotton into snowy ropes of yarn called slivers . then , yarns are sent to the mill , where huge circular knitting machines weave them into sheets of rough grayish fabric treated with heat and chemicals until they turn soft and white . here , the fabric is dipped into commercial bleaches and azo dyes , which make up the vivid coloring in about 70 % of textiles . unfortunately , some of these contain cancer-causing cadmium , lead , chromium , and mercury . other harmful compounds and chemicals can cause widespread contamination when released as toxic waste water in rivers and oceans . technologies are now so advanced in some countries that the entire process of growing and producing fabric barely touches a human hand . but only up until this point . after the finished cloth travels to factories , often in bangladesh , china , india , or turkey , human labor is still required to stitch them up into t-shirts , intricate work that machines just ca n't do . this process has its own problems . bangladesh , for example , which has surpassed china as the world 's biggest exporter of cotton t-shirts , employs 4.5 million people in the t-shirt industry , but they typically face poor conditions and low wages . after manufacture , all those t-shirts travel by ship , train , and truck to be sold in high-income countries , a process that gives cotton an enormous carbon footprint . some countries produce their own clothing domestically , which cuts out this polluting stage , but generally , apparel production accounts for 10 % of global carbon emissions . and it 's escalating . cheaper garments and the public 's willingness to buy boosted global production from 1994 to 2014 by 400 % to around 80 billion garments each year . finally , in a consumer 's home , the t-shirt goes through one of the most resource-intensive phases of its lifetime . in america , for instance , the average household does nearly 400 loads of laundry per year each using about 40 gallons of water . washing machines and dryers both use energy , with dryers requiring five to six times more than washers . this dramatic shift in clothing consumption over the last 20 years , driven by large corporations and the trend of fast fashion has cost the environment , the health of farmers , and driven questionable human labor practices . it 's also turned fashion into the second largest polluter in the world after oil . but there are things we can do . consider shopping secondhand . try to look for textiles made from recycled or organic fabrics . wash clothes less and line dry to save resources . instead of throwing them away at the end of their life , donate , recycle , or reuse them as cleaning rags . and , finally , you might ask yourself , how many t-shirts and articles of clothing will you consume over your lifetime , and what will be their combined impact on the world ?

these pollutants can be carcinogenic , harm the health of field workers , and damage surrounding ecosystems . some t-shirts are made of organic cotton grown without pesticides and insecticides , but organic cotton makes up less than 1 % of the 22.7 million metric tons of cotton produced worldwide . once the cotton bales leave the farm , textile mills ship them to a spinning facility , usually in china or india , where high-tech machines blend , card , comb , pull , stretch , and , finally , twist the cotton into snowy ropes of yarn called slivers .

of the 22.7 million metric tons of cotton produced , ____ is grown organically .

the politics of 19th century europe were messy . ( what 's changed ? ) it was made up of various empires spreading across the world , trying to show each other who was the biggest power . they each built up massive armies to stave off war , thinking that everyone else would be too scared to fight against them , or so they thought ... things all changed when a gang of yugoslav nationalists who did n't like being part of austria-hungary shot the austro-hungarian archduke franz ferdinand while he was in sarajevo . swiftly the austro-hungarian empire declared war on serbia . russia came in to aid serbia , so germany decided to declare war on russia ! knowing that france would go to war with germany , germany decided to attack france quickly and invaded via neutral belgium and luxembourg and because of this , great britain stepped in to stop the germans getting any closer . it was a mess of allegiances and old rivalries with two sides forming the allies and the central powers . and so began what became known at the time as the great war ; the war to end all wars ! a new form of warfare evolved as these fully industrialized armies with engines , machine guns , airplanes and new chemical gas weapons fought against each other . it was the dawn of modern warfare . at the time , national pride was at an all-time high and men were proud to go off and fight for their country . it was seen as a romantic idea to go off and be a hero ! boys as young as 12 managed to lie their way into the army ranks only to discover that it was not such a sweet and honourable thing to die for one 's country ! germany marched on paris but was stopped by the french and both sides dug themselves into trenches in what became known as the western front . on the eastern front , the russians invaded austria-hungary but were stopped in eastern prussia by the germans . the ottoman empire joined in on the site of the central powers in 1914 . more and more nations from all over the world joined the fight as the war spread across europe . trench warfare was quite terrible . each army would dig a long network of trenches in the ground , fortifying the front with barbed wire and sandbags . i was a long stalemate where neither side dared advance on the other . machine guns were a new and very effective weapon . when the time was right , the army would climb up over the top and charge across no-man 's land to the enemy trench and capture it , thus gaining more land and taking another step towards their goal ! at least that was the plan ... spirits were high at least when the first christmas came by . both forces climbed out of their trenches to celebrate christmas together , talk , share stories and play football . when christmas ended , they would climb back into their trenches to become enemies once again . conditions in the trenches were dreadful . soldiers in france and belgium found their feet rotting away from the constant damp . in contrast , australian , new zealand and ottoman soldiers fighting in gallipoli had blisteringly hot trenches where rain and cold were replaced with dehydration and overheating . disease was everywhere in the trenches . 1916 saw a renewed push on the western front from both sides . thousands of french died at verdun as the germans unleashed their chlorine gas . the infamous battle of the somme was a long and grueling battle that lasted from july to november . the first day alone saw over 80,000 men wounded or killed ; mostly british , due to disastrous attacks . fundamental errors and contradictions from the high command led to confusion and unclear plans . in places , soldiers were n't organized in time to charge so by the time that they got going , the artillery had stopped firing on the germans , allowing them to easily fire upon their attackers . planes and artillery were supposed to clear the german barbed wire , but the shrapnel was ineffective against the wire . when the order came to go over the top , thousands of men ran out to their death to be caught on the barbed wire and picked off one by one by the german machine guns . this battle saw the first use of tanks by the british . ultimately , france and britain pushed against germany and gained much ground . by christmas 1916 , no man wanted good cheer wished upon their faceless enemy . during 1916 also , before the somme , irish republicans staged an uprising in dublin in the hopes to catch britain while they were distracted by the war . it was crushed by britain but after executing the rebel leaders irish support for britain and the war dropped , at least in the south of ireland . most irish troops after that came from the protestant north . on the sea britain mined many patches of international water to stop movement of german ships . germany was blockaded . after many naval battles , britain tried to stay in control of the seas , above the water at least ! germany were on the attack with the u-boat submarines adding a new dimension to naval warfare ; they could attack without warning ! they sank many ships including the ship the lusitania and because this broke loads of war rules , it ultimately influenced the united states of america to enter the war ... two years later ! the british pushed up through the arabian peninsula with t.e . lawrence aka lawrence of arabia helping to organize the arab revolt against the ottoman empire . in 1917 , the russians had a series of revolutions . in the february revolution , the tsars were gotten rid of , but russia remained in the war , and the october revolution , the bolsheviks took control and brought power to the people and sowed the seeds for communism in russia . the russians signed a treaty with germany and pulled out of the war causing an initial difficulty for the enemies of the central powers . the allies however became refreshed with reinforcements from the united states of america who eventually decided to enter the war in 1917 after germany tried to convince mexico to attack them . germany made a fierce and effective push before the allies could use their advantage . however , american troops continued to arrive in such great numbers that germany 's army could n't last any longer . the allies pushed up from italy , the balkans , and the middle east putting austria-hungary , bulgaria and the ottoman empire out of the war . as the allies advanced the western front , germany called for an armistice to stop the fighting , bringing victory to the allies and an end to the war . the fighting stopped on the 11th hour of the 11th day of the 11th month , 1918 . it took six months to negotiate terms and it was ultimately decided that the central powers were to pay for the damages they had caused in the war . germany only fully paid off this debt in 2010 . the map of europe was redrawn . soldiers who made it home again were changed men . they were haunted by the horrors which they had seen in the trenches . gas attacks , friends dying by their side , and the constant shelling of enemy artillery ; they were shell-shocked and so many found it impossible to go back to normal life after the trenches . many great poets and writers were inspired by their hell in the trenches such as wilfred owen , jrr tolkien and ernest hemingway of the so-called lost generation ? some survived , many did not . the world was a changed place after the world war . people had seen the death and destruction that could be dealt by mankind . the men who left to become heroes came back scarred , or worse never returned at all . the poppy is used to remember the millions who died in this war as it was just about the only flower to grow in the carnage-ridden wasteland between the trenches . the world was now a darker place . people hoped that it would indeed be the war to end all wars ! unfortunately , they were mistaken ... if you liked this video , please subscribe and you can follow me on twitter at @ johndruddy or find me on facebook through manny man comic and john d ruddy artisty actory guy and if you want to find out more about world war one and also the easter rising of 1916 i 'll be doing an irish tour of the play the rising by joe o ' byrne where we tell the story of the easter rising through the eyes of two friendly foes . billy mckeague , a loyalist from belfast and paddy o'brien , a republican from dublin . the dates are up here and you can find out more on facebook . thanks so much for the support glad you enjoy it !

spirits were high at least when the first christmas came by . both forces climbed out of their trenches to celebrate christmas together , talk , share stories and play football . when christmas ended , they would climb back into their trenches to become enemies once again . conditions in the trenches were dreadful . soldiers in france and belgium found their feet rotting away from the constant damp .

name one of the dangers of the trenches .

without water , a human can only survive for about 100 hours . but there 's a creature so resilient that it can go without it for decades . this one millimeter animal can survive both the hottest and coldest environments on earth , and can even withstand high levels of radiation . this is the tardigrade , and it 's one of the toughest creatures on earth , even if it does look more like a chubby , eight-legged gummy bear . most organisms need water to survive . water allows metabolism to occur , which is the process that drives all the biochemical reactions that take place in cells . but creatures like the tardigrade , also known as the water bear , get around this restriction with a process called anhydrobiosis , from the greek meaning life without water . and however extraordinary , tardigrades are n't alone . bacteria , single-celled organisms called archaea , plants , and even other animals can all survive drying up . for many tardigrades , this requires that they go through something called a tun state . they curl up into a ball , pulling their head and eight legs inside their body and wait until water returns . it 's thought that as water becomes scarce and tardigrades enter their tun state , they start synthesize special molecules , which fill the tardigrade 's cells to replace lost water by forming a matrix . components of the cells that are sensitive to dryness , like dna , proteins , and membranes , get trapped in this matrix . it 's thought that this keeps these molecules locked in position to stop them from unfolding , breaking apart , or fusing together . once the organism is rehydrated , the matrix dissolves , leaving behind undamaged , functional cells . beyond dryness , tardigrades can also tolerate other extreme stresses : being frozen , heated up past the boiling point of water , high levels of radiation , and even the vacuum of outer space . this has led to some erroneous speculation that tardigrades are extraterrestrial beings . while that 's fun to think about , scientific evidence places their origin firmly on earth where they 've evolved over time . in fact , this earthly evolution has given rise to over 1100 known species of tardigrades and there are probably many others yet to be discovered . and because tardigrades are so hardy , they exist just about everywhere . they live on every continent , including antarctica . and they 're in diverse biomes including deserts , ice sheets , the sea , fresh water , rainforests , and the highest mountain peaks . but you can find tardigrades in the most ordinary places , too , like moss or lichen found in yards , parks , and forests . all you need to find them is a little patience and a microscope . scientists are now to trying to find out whether tardigrades use the tun state , their anti-drying technique , to survive other stresses . if we can understand how they , and other creatures , stabilize their sensitive biological molecules , perhaps we could apply this knowledge to help us stabilize vaccines , or to develop stress-tolerant crops that can cope with earth 's changing climate . and by studying how tardigrades survive prolonged exposure to the vacuum of outer space , scientists can generate clues about the environmental limits of life and how to safeguard astronauts . in the process , tardigrades could even help us answer a critical question : could life survive on planets much less hospitable than our own ?

this one millimeter animal can survive both the hottest and coldest environments on earth , and can even withstand high levels of radiation . this is the tardigrade , and it 's one of the toughest creatures on earth , even if it does look more like a chubby , eight-legged gummy bear . most organisms need water to survive .

when a tardigrade dries out what does it do ?

what if electricity could travel forever without being diminished ? what if a computer could run exponentially faster with perfect accuracy ? what technology could those abilities build ? we may be able to find out thanks to the work of the three scientists who won the nobel prize in physics in 2016 . david thouless , duncan haldane , and michael kosterlitz won the award for discovering that even microscopic matter at the smallest scale can exhibit macroscopic properties and phases that are topological . but what does that mean ? first of all , topology is a branch of mathematics that focuses on fundamental properties of objects . topological properties do n't change when an object is gradually stretched or bent . the object has to be torn or attached in new places . a donut and a coffee cup look the same to a topologist because they both have one hole . you could reshape a donut into a coffee cup and it would still have just one . that topological property is stable . on the other hand , a pretzel has three holes . there are no smooth incremental changes that will turn a donut into a pretzel . you 'd have to tear two new holes . for a long time , it was n't clear whether topology was useful for describing the behaviors of subatomic particles . that 's because particles , like electrons and photons , are subject to the strange laws of quantum physics , which involve a great deal of uncertainty that we do n't see at the scale of coffee cups . but the nobel laureates discovered that topological properties do exist at the quantum level . and that discovery may revolutionize materials science , electronic engineering , and computer science . that 's because these properties lend surprising stability and remarkable characteristics to some exotic phases of matter in the delicate quantum world . one example is called a topological insulator . imagine a film of electrons . if a strong enough magnetic field passes through them , each electron will start traveling in a circle , which is called a closed orbit . because the electrons are stuck in these loops , they 're not conducting electricity . but at the edge of the material , the orbits become open , connected , and they all point in the same direction . so electrons can jump from one orbit to the next and travel all the way around the edge . this means that the material conducts electricity around the edge but not in the middle . here 's where topology comes in . this conductivity is n't affected by small changes in the material , like impurities or imperfections . that 's just like how the hole in the coffee cup is n't changed by stretching it out . the edge of such a topological insulator has perfect electron transport : no electrons travel backward , no energy is lost as heat , and the number of conducting pathways can even be controlled . the electronics of the future could be built to use this perfectly efficient electron highway . the topological properties of subatomic particles could also transform quantum computing . quantum computers take advantage of the fact that subatomic particles can be in different states at the same time to store information in something called qubits . these qubits can solve problems exponentially faster than classical digital computers . the problem is that this data is so delicate that interaction with the environment can destroy it . but in some exotic topological phases , the subatomic particles can become protected . in other words , the qubits formed by them ca n't be changed by small or local disturbances . these topological qubits would be more stable , leading to more accurate computation and a better quantum computer . topology was originally studied as a branch of purely abstract mathematics . thanks to the pioneering work of thouless , haldane , and kosterlitz , we now know it can be used to understand the riddles of nature and to revolutionize the future of technologies .

that 's because these properties lend surprising stability and remarkable characteristics to some exotic phases of matter in the delicate quantum world . one example is called a topological insulator . imagine a film of electrons .

topological insulator is a material that conducts electricity ____ .

dating back at least to the time of socrates , some early societies decided that certain disputes , such as whether a person committed a particular crime , should be heard by a group of citizens . several centuries later , trial by jury was introduced to england , where it became a fundamental feature of the legal system , checking the government and involving citizens in decision-making . juries decided whether defendants would be tried on crimes , determined whether the accused defendants were guilty , and resolved monetary disputes . while the american colonies eventually cast off england 's rule , its legal tradition of the jury persisted . the united states constitution instructed a grand jury to decide whether criminal cases proceeded , required a jury to try all crimes , except impeachment , and provided for juries in civil cases as well . yet , in the us today , grand juries often are not convened , and juries decide less than 4 % of criminal cases and less than 1 % of civil cases filed in court . that 's at the same time as jury systems in other countries are growing . so what happened in the u.s. ? part of the story lies in how the supreme court has interpreted the constitution . it 's permitted plea bargaining , which now occurs in almost every criminal case . the way it works is the prosecutor presents the accused with a decision of whether to plead guilty . if they accept the plea , the case wo n't go in front of a jury , but they 'll receive a shorter prison sentence than they 'd get if a jury did convict them . the risk of a much greater prison sentence after a trial can frighten even an innocent defendant into taking a plea . between the 19th century and the 21st century , the proportion of guilty pleas has increased from around 20 % to 90 % , and the numbers continue to grow . the supreme court has permitted the use of another procedure that interferes with the jury called summary judgement . using summary judgement , judges can decide that civil trials are unnecessary if the people who sue have insufficient evidence . this is intended only for cases where no reasonable jury would disagree . that 's a difficult thing to determine , yet usage of summary judgement has stretched to the point where some would argue it 's being abused . for instance , judges grant fully , or in part , over 70 % of employers ' requests to dismiss employment discrimination cases . in other cases , both the person who sues and the person who defends forgo their right to go to court , instead resolving their dispute through a professional arbitrator . these are generally lawyers , professors , or former judges . arbitration can be a smart decision by both parties to avoid the requirements of a trial in court , but it 's often agreed to unwittingly when people sign contracts like employment applications and consumer agreements . that can become a problem . for example , some arbitrators may be biased towards the companies that give them cases . these are just some of the ways in which juries have disappeared . but could the disappearance of juries be a good thing ? well , juries are n't perfect . they 're costly , time-consuming , and may make errors . and they 're not always necessary , like when people can simply agree to settle their disputes . but juries have their advantages . when properly selected , jurors are more representative of the general population and do n't have the same incentives as prosecutors , legislators , or judges seeking reelection or promotion . the founders of the united states trusted in the wisdom of impartial groups of citizens to check the power of all three branches of government . and the jury trial itself has given ordinary citizens a central role in upholding the social fabric . so will the jury system in the u.s. survive into the future ?

part of the story lies in how the supreme court has interpreted the constitution . it 's permitted plea bargaining , which now occurs in almost every criminal case . the way it works is the prosecutor presents the accused with a decision of whether to plead guilty .

a judge can prevent a case from going to a jury in a civil case by ordering __________ .

oh , excuse me ! have you ever yawned because somebody else yawned ? you are n't especially tired , yet suddenly your mouth opens wide and a big yawn comes out . this phenomenon is known as contagious yawning . and while scientists still do n't fully understand why it happens , there are many hypotheses currently being researched . let 's take a look at a few of the most prevalent ones , beginning with two physiological hypotheses before moving to a psychological one . our first physiological hypothesis states that contagious yawning is triggered by a specific stimulus , an initial yawn . this is called fixed action pattern . think of fixed action pattern like a reflex . your yawn makes me yawn . similar to a domino effect , one person 's yawn triggers a yawn in a person nearby that has observed the act . once this reflex is triggered , it must run its course . have you ever tried to stop a yawn once it has begun ? basically impossible ! another physiological hypothesis is known as non-conscious mimicry , or the chameleon effect . this occurs when you imitate someone 's behavior without knowing it , a subtle and unintentional copycat maneuver . people tend to mimic each other 's postures . if you are seated across from someone that has their legs crossed , you might cross your own legs . this hypothesis suggests that we yawn when we see someone else yawn because we are unconsciously copying his or her behavior . scientists believe that this chameleon effect is possible because of a special set of neurons known as mirror neurons . mirror neurons are a type of brain cell that responds equally when we perform an action as when we see someone else perform the same action . these neurons are important for learning and self-awareness . for example , watching someone do something physical , like knitting or putting on lipstick , can help you do those same actions more accurately . neuroimaging studies using fmri , functional magnetic resonance imaging , show us that when we seem someone yawn or even hear their yawn , a specific area of the brain housing these mirror neurons tends to light up , which , in turn , causes us to respond with the same action : a yawn ! our psychological hypothesis also involves the work of these mirror neurons . we will call it the empathy yawn . empathy is the ability to understand what someone else is feeling and partake in their emotion , a crucial ability for social animals like us . recently , neuroscientists have found that a subset of mirror neurons allows us to empathize with others ' feelings at a deeper level . ( yawn ) scientists discovered this empathetic response to yawning while testing the first hypothesis we mentioned , fixed action pattern . this study was set up to show that dogs would enact a yawn reflex at the mere sound of a human yawn . while their study showed this to be true , they found something else interesting . dogs yawned more frequently at familiar yawns , such as from their owners , than at unfamiliar yawns from strangers . following this research , other studies on humans and primates have also shown that contagious yawning occurs more frequently among friends than strangers . in fact , contagious yawning starts occurring when we are about four or five years old , at the point when children develop the ability to identify others ' emotions properly . still , while newer scientific studies aim to prove that contagious yawning is based on this capacity for empathy , more research is needed to shed light on what exactly is going on . it 's possible that the answer lies in another hypothesis altogether . the next time you get caught in a yawn , take a second to think about what just happened . were you thinking about a yawn ? did someone near you yawn ? was that person a stranger or someone close ? and are you yawning right now ? ( yawn ) ( lip smacking )

you are n't especially tired , yet suddenly your mouth opens wide and a big yawn comes out . this phenomenon is known as contagious yawning . and while scientists still do n't fully understand why it happens , there are many hypotheses currently being researched .

which scientific theory describes contagious yawning as a ‘ reflex ’ action ?

perfumers can learn to distinguish individual odors in a fragrance made of hundreds of scents . tea experts have been known to sniff out not just the location where a tea was from , but the season of harvest and whether it was planted by a plum tree . and the new york city transit authority once had an employee responsible only for sniffing out gas leaks in the subway system . can just anyone learn to smell with the sensitivity of those experts ? for most of us , what we smell is largely involuntary , whether it 's garbage behind a restaurant , the shampoo of the woman leaving an elevator as you enter , or a bakery 's fresh-made bread . with a few million olfactory receptors in our noses , we clearly do n't lack the ability to smell well . we just might not always pay close enough attention . that 's a shame because we may be missing opportunities to make strong emotional connections . smells are powerfully linked to emotions and can awaken memories of places we 've long ago left and people we 've loved . but fortunately , it is possible to train our brains to smell better . for example , helen keller was able to recognize a person 's work , and in her words , distinguish the carpenter from the iron worker , the artist from the mason or the chemist , by a simple inhale . follow these steps and you too can change the way the world smells to you . first , stick your nose in it . some animals that are known to be great smellers , like dogs who can sniff out explosives and pigs who can find truffles underground , put their noses right at the place they want to smell . human noses , meanwhile , are casting around in the middle of the air , giving us an anatomical disadvantage . so bring your nose close to the world around you . the ground , surfaces , objects , the food in your hand . get close to your dog , your partner , the book you 're reading . not only will your nose be closer to the odor source , but the warmth of your breath will make odors easier to smell . second , sniff like you mean it . smelling actually happens way up near the bridge of our noses in a postage stamp-sized square of tissue called the olfactory epithelium . when we sniff , odor molecules are sucked up into our nostrils until they hit this tissue where they combine to our olfactory , or scent , receptors . when we inhale normally , only a little air makes it there . but one or two solid sharp sniffs will ensure that more air gets to your smell receptors . after just a few more sniffs , the receptors , which are best at noticing new smells , turn off temporarily . so you can give your nose a rest and sniff again later . finally , dwell on the smell . most smells pass by us with little attention , but simply noticing what you 're smelling and by trying to describe it , name it , and locate its source , you can expand your vocabulary of smells . when an odor molecule binds to a scent receptor , it sends an electrical signal from the sensory neurons to our brain 's olfactory bulbs . the signal then continues to other areas of the brain , where it 's integrated with taste , memory , or emotional information before registering to us as a smell . fmri research shows that the extra time spent focusing on scent changes the brain of experienced smellers . for them , perceiving and imagining odors becomes more automatic than for non-experts . to get started yourself , take ingredients from your kitchen : spices , vanilla , or fruit , but never anything toxic . close your eyes and have someone bring them under your nose . sniff and try to name the source . over time , you 'll begin to appreciate nuances in familiar odors and recognize characteristics of new and unusual smells . the perfumer has practiced these steps enough to become an artist of odor , but even if you never pursue smelling to that degree , the spectacular result of an unspectacular action will change how you sense and experience your days .

when we sniff , odor molecules are sucked up into our nostrils until they hit this tissue where they combine to our olfactory , or scent , receptors . when we inhale normally , only a little air makes it there . but one or two solid sharp sniffs will ensure that more air gets to your smell receptors .

you want to become better at smelling . practice makes perfect . explain .

how is it that so many intergalactic species in movies and tv just happen to speak perfect english ? the short answer is that no one wants to watch a starship crew spend years compiling an alien dictionary . but to keep things consistent , the creators of star trek and other science-fiction worlds have introduced the concept of a universal translator , a portable device that can instantly translate between any languages . so is a universal translator possible in real life ? we already have many programs that claim to do just that , taking a word , sentence , or entire book in one language and translating it into almost any other , whether it 's modern english or ancient sanskrit . and if translation were just a matter of looking up words in a dictionary , these programs would run circles around humans . the reality , however , is a bit more complicated . a rule-based translation program uses a lexical database , which includes all the words you 'd find in a dictionary and all grammatical forms they can take , and set of rules to recognize the basic linguistic elements in the input language . for a seemingly simple sentence like , `` the children eat the muffins , '' the program first parses its syntax , or grammatical structure , by identifying the children as the subject , and the rest of the sentence as the predicate consisting of a verb `` eat , '' and a direct object `` the muffins . '' it then needs to recognize english morphology , or how the language can be broken down into its smallest meaningful units , such as the word muffin and the suffix `` s , '' used to indicate plural . finally , it needs to understand the semantics , what the different parts of the sentence actually mean . to translate this sentence properly , the program would refer to a different set of vocabulary and rules for each element of the target language . but this is where it gets tricky . the syntax of some languages allows words to be arranged in any order , while in others , doing so could make the muffin eat the child . morphology can also pose a problem . slovene distinguishes between two children and three or more using a dual suffix absent in many other languages , while russian 's lack of definite articles might leave you wondering whether the children are eating some particular muffins , or just eat muffins in general . finally , even when the semantics are technically correct , the program might miss their finer points , such as whether the children `` mangiano '' the muffins , or `` divorano '' them . another method is statistical machine translation , which analyzes a database of books , articles , and documents that have already been translated by humans . by finding matches between source and translated text that are unlikely to occur by chance , the program can identify corresponding phrases and patterns , and use them for future translations . however , the quality of this type of translation depends on the size of the initial database and the availability of samples for certain languages or styles of writing . the difficulty that computers have with the exceptions , irregularities and shades of meaning that seem to come instinctively to humans has led some researchers to believe that our understanding of language is a unique product of our biological brain structure . in fact , one of the most famous fictional universal translators , the babel fish from `` the hitchhiker 's guide to the galaxy '' , is not a machine at all but a small creature that translates the brain waves and nerve signals of sentient species through a form of telepathy . for now , learning a language the old fashioned way will still give you better results than any currently available computer program . but this is no easy task , and the sheer number of languages in the world , as well as the increasing interaction between the people who speak them , will only continue to spur greater advances in automatic translation . perhaps by the time we encounter intergalactic life forms , we 'll be able to communicate with them through a tiny gizmo , or we might have to start compiling that dictionary , after all .

but to keep things consistent , the creators of star trek and other science-fiction worlds have introduced the concept of a universal translator , a portable device that can instantly translate between any languages . so is a universal translator possible in real life ? we already have many programs that claim to do just that , taking a word , sentence , or entire book in one language and translating it into almost any other , whether it 's modern english or ancient sanskrit .

why would semantics play an important role in a machine translator ?

so this is manganese metal . you know , very often in chemistry we use manganese in the form of permanganate as an oxidizing agent but this is manganese metal . manganese is right in the middle of the row of transition metals and it has 5 electrons , which can give it a really very rich chemistry . so here you can see it is a brand new sample although the bottle looks very , very old , it is 100grams . so i am going to pour a small amount of manganese out , so that we can have a closer look . one of the main uses of manganese at the moment is as a catalyst for making the plastic which you find in plastic water bottles . you can see my big display of water bottles up there . and manganese is a key catalyst in the reaction between xylene , which is the raw material which you get from crude oil to make terephthalic acid which is one of the components in this plastic . and the reason it is important is that manganese can add and lose electrons which help in the reaction between xylene and oxygen . there is some paper on the top . manganese is also important in old batteries , the older batteries that you used in torches , the sort that leaked , contained manganese dioxide . so here we have the manganese and we are going to pour a small amount out so that we can have a look at this element . and you can see how the colour refracts off the top , really a quite lovely sample of the manganese metal itself . so we are looking at manganese crystals growing from the surface because this material would have been made from a high temperature , crystal growing-type process . so you can see the manganese is growing and seeding new crystallites of the surface - seeding off in every direction . it ’ s cool .

so this is manganese metal . you know , very often in chemistry we use manganese in the form of permanganate as an oxidizing agent but this is manganese metal . manganese is right in the middle of the row of transition metals and it has 5 electrons , which can give it a really very rich chemistry . so here you can see it is a brand new sample although the bottle looks very , very old , it is 100grams .

manganese has a very rich chemistry . what are its oxidation states ?

[ ♪sustained note♪ ] [ flag flapping in breeze ] [ path of freedom ] [ ♪ music ♪ ] [ prisoners chattering ] [ ♪ music ♪ ] - this is a tough guy world , and we have to control all of their movement and their behavior [ roberta richman - rhode island dept . of corrections ] because that 's the way you keep an institution safe for everybody who lives in it . [ ♪ music ♪ ] we have everybody here— murderers and rapists , sex offenders , drug addicts— everybody . [ 1 out of every 100 americans is currently behind bars ] my name is dennis . i 'm 52 years old . i 'm serving a 15-year sentence for assaulting my wife . my name is louis , 35 . i sold narcotics [ clears throat ] since i was about 13 or so . my name is juan . i 'm 34 years old . i 'm here for second degree murder . yeah . sadly , this is my charge . my name is celine . i 'm 39 . i 'll be 40 soon . i was given a life term . [ ♪ music ♪ ] a lot of times what lands people in prison [ fleet maull - prison mindfulness institute ] and what brings them back is a lack of good problem-solving skills and good communication skills . [ ♪ music ♪ ] [ richman ] fleet approached us asking if he could do some work in here . we were challenged . our union wanted to know how we could possibly bring an ex-offender in . [ maull ] i served 14½ years on a 25-year , no parole sentence . hello . [ ♪ music ♪ ] having served 14 years boosts his credibility— boosts his credibility with inmates . how 's your week been ? - it 's good . [ maull ] yeah ? good . what 's up ? yeah . hey . welcome . when i got locked up , i really hit a wall of just seeing the craziness of my life path up until then and the incredible selfish decisions i 'd been making . my son was 9 years old . he was going to grow up without his dad . and i was just so deeply full of remorse and regret that i just literally started practicing meditation like my hair was on fire . so i became extremely motivated to turn my life around . [ ♪ music ♪ ] and so i was living the life of this prison monk . [ ♪ music ♪ ] i was sourcing a meditation group twice a week in the chapel . [ ♪ music ♪ ] i started receiving letters from prisoners while i was in prison . i had published some articles ; people knew about me out in the world a little bit , and they started sending some of these letters to me thinking i would know what to do with them . i worked in the education department , and i had access to a copy machine . i would copy articles out of books , and i 'd put together a little thing and i 'd send it off to a prisoner . so it started off that way , and i decided it was a much bigger deal than i could do from my prison cells . i think we have a co-creative relationship with our life . we ca n't control other people , we do n't control life , but is there some relationship between what we put out and what comes back ? freedom before i came here was just another word . i had never been to prison before . all you know is what the media and the movies say about prison— `` take care of yourself , man . '' `` somebody 's going to try to take your manhood or something . '' you know what i mean ? i 'm thinking i 'm going to come in here and fight the world . [ maull ] in a prison like moran , there 's a serious conflict waiting around any corner . it 's an environment where people 's worst behaviors are just right there just under the surface . [ ♪ music ♪ ] when i first came in , i fought with officers , would beat up anyone , would do the unthinkable just because . [ dennis ] it 's a vicious cycle because once you come to prison your life just keeps tumbling , tumbling , tumbling , and it 's like a never-ending wall that wo n't stop building unless you find some way to get over that wall or at least in front of it . [ richman ] what circumstances did they have to survive on the street to bring them to where they are now ? do we want to save those lives , or do we want to discard them ? the crimes i committed , i brought shame to not only myself but to those who i love . so i 'm just really trying to do something to get out of that cycle . somebody 's given us an opportunity just to meditate and connect ourselves , and that 's golden . so sit up with that good posture , just rest your hands on your legs , and just take a moment to just feel . [ ♪ music ♪ ] [ richman ] i 've always thought that the people who survive are so much stronger than i could ever be . i asked fleet how he survived and thrived the way he has . he credits meditation for having given him the strength to live his life in prison and come out not as much the worse for wear as most people do . i do n't have a release date . so i can only go home when they decide i can . so i learned to live day by day , and that helped me to deal with prison , and i could only do that being in the moment , being in the now . [ ♪ music ♪ ] it 's like if i do n't like what 's going on , what can i do to shift it ? if i do n't like the relationship i have with my boss or with one of the cos or something , could i approach that person in a different way ? can i get creative about what i 'm doing to bring about a shift in the way things are— in other words , owning my own situation . so how do you resolve that ? i take a breath and then [ chuckles ] i step back . really , you have to . [ maull ] then suddenly get that there 's this whole thing there that they thought was who they are . that 's the only reality they knew . suddenly they get to step outside of that a little bit . you just see the lights go on . it 's like this sudden illumination . it 's like a mini enlightenment of sorts . and that 's very powerful . that 's what keeps me coming . the reality of it is i 'm living life , and meditation it has brought a new perspective in the way that it gave me like a tool to really look inside myself and change the way i am . [ richman ] people do n't understand the value of what they call the soft stuff , and i sometimes think without the soft stuff , no matter how much hard stuff you have , you 're bound to fail . you can live your life . you can be yourself . you can show others that this is n't a place to breed a better criminal ; this could actually be a place to breed a better person . you 're here because the way that you were did n't work . so why not be better ? [ prisoners chattering ] [ richman ] the people in prison are us . they 're not monsters . and more importantly , whether we want them to or not , they 're getting out . so do you want them to come out angrier and meaner and more dangerous than they were when they came in , or do you want to do whatever you can to change their behavior while they 're here ? we need people to see and experience prisoners stepping out of that culture and doing something transformative with their lives , and then people will start to have faith , people will see people coming back to their community and they realize these are human beings and that human beings ' lives have value and they 're not expendable . [ ♪ music ♪ ] [ this year 700,000 people will return home from prison ] [ ♪ music ♪ ] [ directed by emmanuel vaughan-lee , produced by dorothee royal-hedinger ] [ cinematography by elias koch , edited by adam loften , sound recording by emmanuel vaughan-lee ] [ music by h. scott salinas , sound mix by d. chris smith ] [ www.globalonenessproject.org ]

it 's an environment where people 's worst behaviors are just right there just under the surface . [ ♪ music ♪ ] when i first came in , i fought with officers , would beat up anyone , would do the unthinkable just because . [ dennis ] it 's a vicious cycle because once you come to prison your life just keeps tumbling , tumbling , tumbling , and it 's like a never-ending wall that wo n't stop building unless you find some way to get over that wall or at least in front of it .

how would you summarize the prisoners ' reflections about meditation ?

pretty much as long as humans have looked up at the night sky , we ’ ve been studying astronomy . in all this time , we ’ ve learned so much about the universe beyond our solar system , and have found lots of exoplanets orbiting other stars . but there ’ s a lot that scientists still don ’ t know . in fact , three relatively recent exoplanet discoveries are completely baffling researchers because , according to what we know about astronomy , they shouldn ’ t exist ! the first of these planets is called kepler-78b , which was discovered using data from nasa ’ s kepler space telescope , and orbits a star about 400 light years away from earth . based on changes in its star ’ s light , astronomers calculated that kepler-78b ’ s radius is about 1.2 times the radius of earth and it ’ s around 1.7 times as massive as the earth . this means it also has a similar density to the earth , so the researchers think its composition is similar , too , with lots of rock and iron . but that ’ s where the similarities stop . kepler-78b is about 100 times closer to its star than the earth is to the sun , and its surface temperatures might even get up to 3,100 kelvin . basically , it ’ s kind of like earth … if earth was a blazing inferno . this planet ’ s super close orbit to its host star means that a year only lasts 8.5 hours . and scientists don ’ t understand how kepler-78b even exists , because it doesn ’ t fit any of the current theories of planetary formation it ’ s just too close to its star . see , when kepler-78b was first forming from the gas and dust-filled protoplanetary disk , its host star was even larger . so if the planet was orbiting where it is now , it would ’ ve been inside its star , which is ... impossible . another option is that it formed farther away and migrated closer , but scientists think that ’ s pretty unlikely , since it probably would ’ ve kept going and plummeted into the star . as of now , it ’ s a mystery . the main thing we do know about kepler-78b is that it ’ ll probably only be around for another three billion years or so . it ’ ll move closer and closer to its host star , until the gravity eventually tears it apart . our next mysterious planet is called kepler-10c , which was also detected using data from the kepler space telescope , and is about 560 light years away from us . it ’ s radius isn ’ t all that special . it ’ s only about 2.3 times the radius of the earth . and initially , because of its size , scientists predicted that kepler-10c would have a thick , gaseous atmosphere , making it like a mini-neptune . instead , they found a planet with a mass that might be between 14-17 times the earth ’ s , which suggests that it ’ s a really dense rocky planet without much of an atmosphere . a mass that large is basically unheard of in a planet that size , which is why astronomers dubbed it a mega-earth . which , y ’ know , sounds pretty cool . based on our current understanding of planets , one this massive without an atmosphere shouldn ’ t even exist . theoretically , it would ’ ve grabbed a bunch of nearby lighter elements with its huge gravitational force as the star system was forming , and turned into a gas giant like jupiter . but it probably never even had an atmosphere , because if it did at some point , it would ’ ve held onto it . so , right now , scientists are just left with another giant rock in space that they can ’ t really explain . last but not least , we have a gas giant named hd 106906 b , which is 11 times as massive as jupiter , and discovered using data from the hubble space telescope and the magellan telescope in chile . this planet orbits a really young star 300 light years away from earth . the system is only 13 million years old . but that ’ s not what makes it weird . see , hd 106906 b orbits its star at a distance of 650 astronomical units . that ’ s more than 20 times the average distance between the sun and neptune . a planet that far away from its host star shouldn ’ t have had enough gaseous and rocky materials to grow that huge , especially in such a relatively short period of time . but , somehow , it exists . some researchers think it might have formed inside the dust-filled debris disk surrounding its host star , and got kicked out later , but they ’ re still not sure . a recent study seems to support this idea , suggesting that the planet might have even captured some of that dusty material , and might be surrounded by a ring or shroud . but that ’ s just one hypothesis and , until astronomers get more data , the planet is still an enigma . these three planets are just a drop in the bucket that is our universe , and we still have so much to learn . it ’ s really the strangest discoveries that make astronomy so cool . every time we start to think we understand how certain things work , like planetary formation , amazing surprises get thrown our way . thanks for watching this episode of scishow space , and a special thank you to all of our patrons on patreon . if you ’ d like to support more videos like this one , please go to patreon.com/scishow . and don ’ t forget to go to youtube.com/scishowspace and subscribe !

kepler-78b is about 100 times closer to its star than the earth is to the sun , and its surface temperatures might even get up to 3,100 kelvin . basically , it ’ s kind of like earth … if earth was a blazing inferno . this planet ’ s super close orbit to its host star means that a year only lasts 8.5 hours .

why is kepler-10c referred to as `` mega earth '' ?

every chicken was once an egg , every oak tree an acorn , every frog a tadpole . the patch of mold on that old piece of bread in the back of your fridge , not so long ago that was one , solitary cell . even you were once but a gleam in your parents ' eyes . all these organisms share the same basic goal : to perpetuate their own existence . all lifeforms that we 've discovered so far stay alive by using basically the same rules , materials , and machinery . imagine a factory full of robots . these robots have two missions : one , keep the factory running , and two , when the time is right , set up an entirely new factory . to do those things , they need assembly instructions , raw materials , plenty of energy , a few rules about when to work normally , when to work quickly , or when to stop , and some exchange currencies because even robots need to get paid . each factory has a high security office with blueprints for all the possible factory configurations and complete sets of instructions to make all the different types of robots a factory could ever need . special robots photocopy these instructions and send them off to help make the building blocks of more robots . their colleagues assemble those parts into still more robots , which are transported to the right location in the factory and given the tools they need to start working . every robot draws energy from the central power plant , a giant furnace that can burn regular fuel but also scrap materials if not enough regular fuel is available . certain zones in the factory have harsher working conditions , so these areas are walled off . but the robots inside can at least communicate with the rest of the factory through specialized portals embedded directly into the walls . and as you 've probably figured out , what we 're describing here is a cell . the high security office is the nucleus . it stores the blueprints and instructions as deoxyribonucleic acid , or dna . the photocopied instructions are rna . the robots themselves are mostly proteins built from amino acids , but they 'll often use special tools that are , or are derived from , vitamins and minerals . the walls between factory zones and around the factory itself are mostly made up of lipids , a.k.a . fats . in most organisms , the primary fuel source are sugars , but in a pinch , fats and proteins can be broken down and burned in the furnace as well . the portals are membrane proteins which allow very specific materials and information to pass through the walls at the right times . many interactions between robot proteins require some kind of push , think robot minimum wage . a few small but crucial forms of money are transferred between proteins to provide this push . electrons , protons , oxygen , and phosphate groups are the main chemical currencies , and they 're kept in small molecular wallets or larger tote bags to keep them safe . this is biochemistry , the study of how every part of the factory interacts to keep your life running smoothly in the face of extreme challenges . maybe there 's too much fuel ; your body will store the excess as glycogen or fat . maybe there 's not enough ; your body will use up those energy reserves . maybe a virus or bacteria tries to invade ; your body will mobilize the immune system . maybe you touched something hot or sharp ; your nerves will let you know so you can stop . maybe it 's time to create a new cell or a new person . amazingly , oak trees , chickens , frogs , and , yes , even you share so many of the same basic robot and factory designs that biochemists can learn a lot about all of them all at the same time .

electrons , protons , oxygen , and phosphate groups are the main chemical currencies , and they 're kept in small molecular wallets or larger tote bags to keep them safe . this is biochemistry , the study of how every part of the factory interacts to keep your life running smoothly in the face of extreme challenges . maybe there 's too much fuel ; your body will store the excess as glycogen or fat .

what is the distinguishing characteristic of life ? is it consciousness ? is it growth ? is it fertility ( the ability to reproduce ) ? try and find examples of living things that are not conscious , or of inanimate objects that grow , or animals that are born sterile ( believe it or not , there are relatively common examples of all three ! ) . another definition of life is “ the ability to temporarily fight off the tendency towards increasing entropy. ” find the physicist closest to you and ask them what they think of that definition ( you ’ ll also probably want them to explain entropy ) . how would you define life ?

it 's a good day to be a pirate . amaro and his four mateys , bart , charlotte , daniel , and eliza have struck gold : a chest with 100 coins . but now , they must divvy up the booty according to the pirate code . as captain , amaro gets to propose how to distribute the coins . then , each pirate , including amaro himself , gets to vote either yarr or nay . if the vote passes , or if there 's a tie , the coins are divided according to plan . but if the majority votes nay , amaro must walk the plank and bart becomes captain . then , bart gets to propose a new distribution and all remaining pirates vote again . if his plan is rejected , he walks the plank , too , and charlotte takes his place . this process repeats , with the captain 's hat moving to daniel and then eliza until either a proposal is accepted or there 's only one pirate left . naturally , each pirate wants to stay alive while getting as much gold as possible . but being pirates , none of them trust each other , so they ca n't collaborate in advance . and being blood-thirsty pirates , if anyone thinks they 'll end up with the same amount of gold either way , they 'll vote to make the captain walk the plank just for fun . finally , each pirate is excellent at logical deduction and knows that the others are , too . what distribution should amaro propose to make sure he lives ? pause here if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 if we follow our intuition , it seems like amaro should try to bribe the other pirates with most of the gold to increase the chances of his plan being accepted . but it turns out he can do much better than that . why ? like we said , the pirates all know each other to be top-notch logicians . so when each votes , they wo n't just be thinking about the current proposal , but about all possible outcomes down the line . and because the rank order is known in advance , each can accurately predict how the others would vote in any situation and adjust their own votes accordingly . because eliza 's last , she has the most outcomes to consider , so let 's start by following her thought process . she 'd reason this out by working backwards from the last possible scenario with only her and daniel remaining . daniel would obviously propose to keep all the gold and eliza 's one vote would not be enough to override him , so eliza wants to avoid this situation at all costs . now we move to the previous decision point with three pirates left and charlotte making the proposal . everyone knows that if she 's outvoted , the decision moves to daniel , who will then get all the gold while eliza gets nothing . so to secure eliza 's vote , charlotte only needs to offer her slightly more than nothing , one coin . since this ensures her support , charlotte does n't need to offer daniel anything at all . what if there are four pirates ? as captain , bart would still only need one other vote for his plan to pass . he knows that daniel would n't want the decision to pass to charlotte , so he would offer daniel one coin for his support with nothing for charlotte or eliza . now we 're back at the initial vote with all five pirates standing . having considered all the other scenarios , amaro knows that if he goes overboard , the decision comes down to bart , which would be bad news for charlotte and eliza . so he offers them one coin each , keeping 98 for himself . bart and daniel vote nay , but charlotte and eliza grudgingly vote yarr knowing that the alternative would be worse for them . the pirate game involves some interesting concepts from game theory . one is the concept of common knowledge where each person is aware of what the others know and uses this to predict their reasoning . and the final distribution is an example of a nash equilibrium where each player knows every other players ' strategy and chooses theirs accordingly . even though it may lead to a worse outcome for everyone than cooperating would , no individual player can benefit by changing their strategy . so it looks like amaro gets to keep most of the gold , and the other pirates might need to find better ways to use those impressive logic skills , like revising this absurd pirate code .

one is the concept of common knowledge where each person is aware of what the others know and uses this to predict their reasoning . and the final distribution is an example of a nash equilibrium where each player knows every other players ' strategy and chooses theirs accordingly . even though it may lead to a worse outcome for everyone than cooperating would , no individual player can benefit by changing their strategy .

what is the final distribution ?

is there a disease that makes us love cats , and do you have it ? maybe , and it 's more likely than you 'd think . we 're talking about toxoplasmosis , a disease caused by toxoplasma gondii . like all parasites , toxoplasma lives at the expense of its host , and needs its host to produce offspring . to do that , toxo orchestrates a brain manipulation scheme involving cats , their rodent prey , and virtually all other birds and mammals , including humans . documented human infections go as far back as ancient egypt . we found samples in mummies . today , about a third of the world 's population is infected , and most of them never even know it . in healthy people , symptoms often do n't show up at all . when they do , they 're mild and flu-like . but those are just the physical symptoms . toxoplasma also nestles into our brains and meddles with our behavior behind the scenes . to understand why , let 's take a look at the parasite 's life cycle . while the parasite can multiply in practically any host , it can only reproduce sexually in the intestines of cats . the offspring , called oocysts , are shed in the cat 's feces . a single cat can shed up to a hundred million oocysts . if another animal , like a mouse , accidentally ingests them , they 'll invade the mouse 's tissues and mature to form tissue cysts . if the mouse gets eaten by a cat , the tissue cysts become active and release offspring that mate to form new oocysts , completing the cycle . but there 's a problem . a mouse 's natural desire to avoid a cat makes it tough to close this loop . toxoplasma has a solution for that . the parasites invade white blood cells to hitch a ride to the brain where they seem to override the innate fear of predators . infected rodents are more reckless and have slower reaction times . strangest of all , they 're actually attracted to feline urine , which probably makes them more likely to cross paths with a cat and help the parasite complete its life cycle . how does the parasite pull this off ? although the exact mechanism is n't known , toxo appears to increase dopamine , a brain neurotransmitter that is involved in novelty-seeking behavior . thus , one idea is that toxo tinkers with neurotransmitters , the chemical signals that modulate emotions . the result ? fatal attraction . but mice are n't the only animals that end up with these parasites , and that 's where humans , and all of toxo 's other hosts , come in . we can accidentally ingest oocysts in contaminated water , or unwashed produce , or from playing in sandboxes , or cleaning out litter boxes . this is behind the common recommendation that pregnant women not change cat litter . toxo can cause serious birth defects . we can also get toxo from eating undercooked meat from other animals that picked up some oocysts . and it turns out that toxo can mess with our brains , too . studies have found connections between toxo and schizophrenia , biopolar disorder , obsessive compulsive disorder , and aggression . it also slows reactions and decreases concentration , which may be why one study found that people involved in traffic accidents were almost three times more likely to have toxoplasma . so is toxo manipulating our brains as an evolutionary strategy to get predatory cats to eat us ? or are our brains just similar enough to a rodent 's that the same neurological tricks that lure them in catch us in the net , too ? and is toxo the reason so many people love cats and keep them as pets ? well , the jury 's still out on that one . some recent studies even contradict the idea . regardless , toxoplasma has definitely benefited from humans to become one of the world 's most successful parasites . it 's not just our willingness to let cats on our dining room tables or in our beds . raising livestock and building cities which attract rodents has provided billions of new hosts , and you and your cat may be two of them .

some recent studies even contradict the idea . regardless , toxoplasma has definitely benefited from humans to become one of the world 's most successful parasites . it 's not just our willingness to let cats on our dining room tables or in our beds .

which animals can become infected with toxoplasma ?

there are a lot of ways this marvelous language of ours , english , does n't make sense . for example , most of the time when we talk about more than one of something , we put an s on the end . one cat , two cats . but then , there 's that handful of words where things work differently . alone you have a man ; if he has company , then you 've got men , or probably better for him , women too . although if there were only one of them , it would be a woman . or if there 's more than one goose , they 're geese , but why not lots of mooses , meese ? or if you have two feet , then why do n't you read two beek instead of books . the fact is that if you were speaking english before about a thousand years ago , beek is exactly what you would have said for more than one book . if modern english is strange , old english needed therapy . believe it or not , english used to be an even harder language to learn than it is today . twenty-five hundred years ago , english and german were the same language . they drifted apart slowly , little by little becoming more and more different . that meant that in early english , just like in german , inanimate objects had gender . a fork , gafol , was a woman ; a spoon , laefel , was a man ; and the table they were on , bord , was neither , also called neuter . go figure ! being able to use words meant not just knowing their meaning but what gender they were , too . and while today there are only about a dozen plurals that do n't make sense , like men and geese , in old english , it was perfectly normal for countless plurals to be like that . you think it 's odd that more than one goose is geese ? well , imagine if more than one goat was a bunch of gat , or if more than one oak tree was a field of ack . to be able to talk about any of these , you just had to know the exact word for their plural rather than just adding the handy s on the end . and it was n't always an s at the end either . in merry old english , they could add other sounds to the end . just like more than one child is children , more than one lamb was lambru , you fried up your eggru , and people talked not about breads , but breadru . sometimes it was like sheep is today - where , to make a plural , you do n't do anything . one sheep , two sheep . in old english , one house , two house . and just like today , we have oxen instead of oxes . old english people had toungen instead of tongues , namen instead of names , and if things stayed the way they were , today we would have eyen instead of eyes . so , why did n't things stay the way they were ? in a word , vikings . in the 8th century , scandinavian marauders started taking over much of england . they did n't speak english , they spoke norse . plus , they were grown-ups , and grown-ups are n't as good at learning languages as children . after the age of roughly 15 , it 's almost impossible to learn a new language without an accent and without slipping up here and there as we all know from what language classes are like . the vikings were no different , so they had a way of smoothing away the harder parts of how english worked . part of that was those crazy plurals . imagine running up against a language with eggru and gat on the one hand , and then with other words , all you have to do is add 's ' and get days and stones . would n't it make things easier to just use the 's ' for everything ? that 's how the vikings felt too . and there were so many of them , and they married so many of the english women , that pretty soon , if you grew up in england , you heard streamlined english as much as the real kind . after a while nobody remembered the real kind any more . nobody remembered that once you said doora instead of doors and handa instead of hands . plurals made a lot more sense now , except for a few hold-outs like children and teeth that get used so much that it was hard to break the habit . the lesson is that english makes a lot more sense than you think . thank the ancestors of people in copenhagen and oslo for the fact that today we do n't ask for a handful of pea-night instead of peanuts . although , would n't it be fun , if for just a week or two , we could ?

the fact is that if you were speaking english before about a thousand years ago , beek is exactly what you would have said for more than one book . if modern english is strange , old english needed therapy . believe it or not , english used to be an even harder language to learn than it is today .

why did modern english evolve from its ancestor , old english ?

would mathematics exist if people did n't ? since ancient times , mankind has hotly debated whether mathematics was discovered or invented . did we create mathematical concepts to help us understand the universe around us , or is math the native language of the universe itself , existing whether we find its truths or not ? are numbers , polygons and equations truly real , or merely ethereal representations of some theoretical ideal ? the independent reality of math has some ancient advocates . the pythagoreans of 5th century greece believed numbers were both living entities and universal principles . they called the number one , `` the monad , '' the generator of all other numbers and source of all creation . numbers were active agents in nature . plato argued mathematical concepts were concrete and as real as the universe itself , regardless of our knowledge of them . euclid , the father of geometry , believed nature itself was the physical manifestation of mathematical laws . others argue that while numbers may or may not exist physically , mathematical statements definitely do n't . their truth values are based on rules that humans created . mathematics is thus an invented logic exercise , with no existence outside mankind 's conscious thought , a language of abstract relationships based on patterns discerned by brains , built to use those patterns to invent useful but artificial order from chaos . one proponent of this sort of idea was leopold kronecker , a professor of mathematics in 19th century germany . his belief is summed up in his famous statement : `` god created the natural numbers , all else is the work of man . '' during mathematician david hilbert 's lifetime , there was a push to establish mathematics as a logical construct . hilbert attempted to axiomatize all of mathematics , as euclid had done with geometry . he and others who attempted this saw mathematics as a deeply philosophical game but a game nonetheless . henri poincaré , one of the father 's of non-euclidean geometry , believed that the existence of non-euclidean geometry , dealing with the non-flat surfaces of hyperbolic and elliptical curvatures , proved that euclidean geometry , the long standing geometry of flat surfaces , was not a universal truth , but rather one outcome of using one particular set of game rules . but in 1960 , nobel physics laureate eugene wigner coined the phrase , `` the unreasonable effectiveness of mathematics , '' pushing strongly for the idea that mathematics is real and discovered by people . wigner pointed out that many purely mathematical theories developed in a vacuum , often with no view towards describing any physical phenomena , have proven decades or even centuries later , to be the framework necessary to explain how the universe has been working all along . for instance , the number theory of british mathematician gottfried hardy , who had boasted that none of his work would ever be found useful in describing any phenomena in the real world , helped establish cryptography . another piece of his purely theoretical work became known as the hardy-weinberg law in genetics , and won a nobel prize . and fibonacci stumbled upon his famous sequence while looking at the growth of an idealized rabbit population . mankind later found the sequence everywhere in nature , from sunflower seeds and flower petal arrangements , to the structure of a pineapple , even the branching of bronchi in the lungs . or there 's the non-euclidean work of bernhard riemann in the 1850s , which einstein used in the model for general relativity a century later . here 's an even bigger jump : mathematical knot theory , first developed around 1771 to describe the geometry of position , was used in the late 20th century to explain how dna unravels itself during the replication process . it may even provide key explanations for string theory . some of the most influential mathematicians and scientists of all of human history have chimed in on the issue as well , often in surprising ways . so , is mathematics an invention or a discovery ? artificial construct or universal truth ? human product or natural , possibly divine , creation ? these questions are so deep the debate often becomes spiritual in nature . the answer might depend on the specific concept being looked at , but it can all feel like a distorted zen koan . if there 's a number of trees in a forest , but no one 's there to count them , does that number exist ?

mathematics is thus an invented logic exercise , with no existence outside mankind 's conscious thought , a language of abstract relationships based on patterns discerned by brains , built to use those patterns to invent useful but artificial order from chaos . one proponent of this sort of idea was leopold kronecker , a professor of mathematics in 19th century germany . his belief is summed up in his famous statement : `` god created the natural numbers , all else is the work of man . ''

name at least one mathematical idea or principle that you feel is a strictly man-made application or phenomena .

translator : andrea mcdonough reviewer : jessica ruby imagine a place so dark you ca n't see the nose on your face . eyes opened or closed , it 's all the same because the sun never shines there . up ahead , you see a light . when you creep in to investigate , a blue light flits around you . `` i could watch this forever , '' you think . but you ca n't because the mouth of an anglerfish has just sprung open and eaten you alive . you are just one of many creatures at the bottom of the ocean who learn too late to appreciate the power of bioluminescence . bioluminescence refers to the ability of certain living things to create light . the human body can make stuff like ear wax and toe nails , but these organisms can turn parts of their body into glow sticks . it 's like nature made them ready to rave . why ? in one way or another , bioluminescence improves a living thing 's chances of survival . take the firefly . it 's ability to glow green helps it attract a mate on a warm , summer night , but it 's just one of many living things that can glow . the railroad worm , phrixothrix hirtus , can light up its body in two colors : red and green . would you eat something that looks like an airport runway ? neither would any sensible predator . the flashing lights keep the worm safe . then there 's the deep sea shrimp , acantherphyra purpurea . when it feels threatened , it spews a cloud of glowing goo from its mouth . who does n't run the other way when they 've just been puked on ? plus , that puke attracts bigger predators who want to eat the shrimp 's enemy . so what if you ca n't bioluminesce ? no problem ! there are other ways for living things to make bioluminescence work for them , even if they were n't born with the equipment to glow . let 's revisit the anglerfish moments before it tried to eat you . that glowing bait on top of its head ? it comes from a pocket of skin called the esca . the esca holds bioluminescent bacteria . the anglerfish ca n't glow there by itself , so it holds a sack of glowing bacteria instead . remember the firefly ? it can actually make itself glow . inside its lantern are two chemicals , a luciferin and a luciferase . when firefly luciferase and luciferin mix together in the presence of oxygen and fuel for the cell , called atp , the chemical reaction gives off energy in the form of light . once scientists figured out how the firefly creates its luciferase and luciferin , they used genetic engineering to make this light-producing reaction occur inside other living things that ca n't glow . for example , they inserted the genes , or instructions , for a cell to create firefly luciferase and luciferin into a tobacco plant . once there , the tobacco plant followed the instructions slipped into its dna and lit up like a christmas tree . the beauty of bioluminescence , unlike the light from the sun or an incandescent bulb , is that it 's not hot . it takes place in a range of temperatures that do n't burn a living thing . and unlike a glow stick , which fades out as the chemicals inside get used up , bioluminescent reactions use replenishable resources . that 's one reason engineers are trying to develop bioluminescent trees . just think , if planted on the side of highways , they could light the way , using only oxygen and other freely available , clean resources to run . talk about survival advantage ! that could help our planet live longer . do you find yourself thinking of other ways to put bioluminescence to good use ? that glow stick you swing at a rave may help you find a mate , but how else can bioluminescence improve your survival ? if you start thinking in this way , you have seen the light .

the flashing lights keep the worm safe . then there 's the deep sea shrimp , acantherphyra purpurea . when it feels threatened , it spews a cloud of glowing goo from its mouth . who does n't run the other way when they 've just been puked on ?

the deep sea shrimp , acanthephyra purpurea , spews a bioluminescent cloud when it feels threatened . what purpose does this cloud serve ?

has anyone ever told you , `` stand up straight ! '' or scolded you for slouching at a family dinner ? comments like that might be annoying , but they 're not wrong . your posture , the way you hold your body when you 're sitting or standing , is the foundation for every movement your body makes , and can determine how well your body adapts to the stresses on it . these stresses can be things like carrying weight , or sitting in an awkward position . and the big one we all experience all day every day : gravity . if your posture is n't optimal , your muscles have to work harder to keep you upright and balanced . some muscles will become tight and inflexbile . others will be inhibited . over time , these dysfunctional adaptations impair your body 's ability to deal with the forces on it . poor posture inflicts extra wear and tear on your joints and ligaments , increases the likelihood of accidents , and makes some organs , like your lungs , less efficient . researchers have linked poor posture to scoliosis , tension headaches , and back pain , though it is n't the exclusive cause of any of them . posture can even influence your emotional state and your sensitivity to pain . so there are a lot of reasons to aim for good posture . but it 's getting harder these days . sitting in an awkward position for a long time can promote poor posture , and so can using computers or mobile devices , which encourage you to look downward . many studies suggest that , on average , posture is getting worse . so what does good posture look like ? when you look at the spine from the front or the back , all 33 vertebrae should appear stacked in a straight line . from the side , the spine should have three curves : one at your neck , one at your shoulders , and one at the small of your back . you are n't born with this s-shaped spine . babies ' spines just have one curve like a `` c. '' the other curves usually develop by 12-18 months as the muscles strengthen . these curves help us stay upright and absorb some of the stress from activities like walking and jumping . if they are aligned properly , when you 're standing up , you should be able to draw a straight line from a point just in front of your shoulders , to behind your hip , to the front of your knee , to a few inches in front of your ankle . this keeps your center of gravity directly over your base of support , which allows you to move efficiently with the least amount of fatigue and muscle strain . if you 're sitting , your neck should be vertical , not tilted forward . your shoulders should be relaxed with your arms close to your trunk . your knees should be at a right angle with your feet flat on the floor . but what if your posture is n't that great ? try redesigning your environment . adjust your screen so it 's at or slightly below eyelevel . make sure all parts of your body , like your elbows and wrists , are supported , using ergonomic aids if you need to . try sleeping on your side with your neck supported and with a pillow between your legs . wear shoes with low heels and good arch support , and use a headset for phone calls . it 's also not enough to just have good posture . keeping your muscles and joints moving is extremely important . in fact , being stationary for long periods with good posture can be worse than regular movement with bad posture . when you do move , move smartly . keep anything you 're carrying close to your body . backpacks should be in contact with your back carried symetrically . if you sit a lot , get up and move around on occassion , and be sure to exercise . using your muscles will keep them strong enough to support you effectively , on top of all the other benefits to your joints , bones , brain and heart . and if you 're really worried , check with a physical therapist , because yes , you really should stand up straight .

but what if your posture is n't that great ? try redesigning your environment . adjust your screen so it 's at or slightly below eyelevel .

which types of exercises might be performed in office environment that may help one ’ s posture ?

brady haran : hey there , everyone . today 's video is about richard feynman -- a lot of people 's favorite scientist -- and safe breaking . but i just wanted to point out at the start that most safes , or secure filing cabinets , actually have one dial . and if you 've got a three number combination , for example , you 'll turn that dial in one direction , then the other direction , and then back in the other direction . and that 's how you open it . but the mock up that we 've used in this video -- and it is a mock up , i can assure you . it 's about as far from a safe as you could get . we 've used three dials . that kind of makes things a bit more visual , a bit easier to understand looking at it in that way . but in most cases , the sort of safes we 're talking about will actually be using one dial . i do n't want to get all the safe enthusiasts out there too fired up and angry in the comments section . but for now , here 's professor bowley with his pretend safe and the story of richard feynman and his world war ii safe cracking . professor roger bowley : i 'm talking about feynman and how he managed to crack safes when he was working on the atomic bomb project in los alamos in the early '40s . his wife had died . so early in the 1940s , his wife died . and he was stuck in the middle of los alamos , not able to get out . it was a sort of desert area around there . he was stuck with lots of other theoretical physicists . so he needed something for amusement . and as a hobby , he tried cracking open all the safes in los alamos . now , they had new , purpose built safes with locks on them made by the mosler lock company . you can imagine 100 numbers for this , 100 numbers for that , 100 numbers for that -- a million , a million possible settings . and if you fiddle them around , it 'll take about five seconds to do it . so if you tried to crack it , it will take you about 60 days . on the average , it 'd be 30 days , but 60 days if you screw up and it takes the last one to open it . well , feynman was a group leader . so he was given one of these in his office to keep all the top secret files that he might come up with . so he knew how this worked mechanically , because he fiddled around with it . he 'd just fidget with anything . he wanted to know how it worked . and he found by trial and error , suppose the number should be 20 , it was set at . actually , it started at 25 , and a lot of people did n't change it from 25 , naught , 25 . that was the default . and if he wanted to crack the safe , a lot of times , people left it in the default setting , because it 's the easiest one to remember . suppose he set it at 20 . now , he found that if he tried to set it at 20 and it opened , he could also set it to 21 and it would open , or 22 . there was some slack on this . this was not mechanically perfect . so there was a bit of tolerance , plus or minus 2 on every single number , which meant that if you set it at 20 , it could be 21 or 22 or 19 or 18 -- and the same for this dial and the same for this dial . so now , if you go through all the combinations , you only have to do 3 , 8 , 13 and so on -- every fifth one -- to make sure you cover them all . now , there are only 20 settings for this , 20 for that , and 20 for that . so automatically , that 's gone down , oh , i ca n't do it . can you do it in your head , brady ? it 's really quite difficult . 8,000 different settings -- now , that becomes doable mechanically . it will take you something like 10 hours working solidly overnight . and you could do it . and he could do that . he worked out how to do it . he found out other ways of doing this . he found that most people will set a birthday , an anniversary , some well-defined date that -- i do n't know , the independence day in the united states of america , whatever . and it would not be an ordinary number , because if it 's going to be , say , my birthday , which is the 21st of april if anybody wants to send me presents . there 's the 21st . 04 -- 04 is there . and i 'm born in 1946 , which is down there . so for the top one , which is the days of the month , there are typically 30 days in a month . so let 's suppose there are just 30 and never 31 . 30 days in the month , you would need to set it in six different positions . now , for the months , there 's 12 months in the year , so you may need not two , but three for that . so now , we 've got six settings here , three settings there . and for the year -- well , now , the year , if it 's some date , it 's going to be something in the past . so how long back in the past is somewhat arbitrary . but suppose 45 would do , and then it would be 9 . he was doing it 1942 or '43 or '44 . all right . so the test would be somewhere around there . so 45 is a natural number to look at , because then you do n't have to go back into the previous century . 6 for this one , 3 for this one , and 9 for that one . and you multiply them together . and you get out 162 . so that 's 162 different settings . five seconds for each , 162 -- that 's 800 seconds . it 's about 12 minutes . so he could go in and if somebody had chosen one of those dates , instead of having 8,000 , he 's got 162 . and he can do it in 12 minutes . on the average , it will be six minutes , because he might be reach it in the first go or he might reach it after 12 minutes . but he would only require 12 minutes . so he would go in and make a big fuss of going into the office and say , i 'm not going to show the secrets . these are top secret stuff . i do n't want everybody to know my secrets . and he 'd carry in a bag with tools -- screwdrivers , picks , all sorts of things that people would think you crack safes with -- shut the door , and in 12 minutes , he would do it . he 'd take a magazine in with him . sometimes , he 'd get it done straight away and he 'd do some exercise and wait for 20 minutes just to make everybody believe it was tough work doing this . and then he 'd come out with a bit of sweat on his brow , saying , that was hard work . so those were the main techniques that he used . 162 means that this is n't safe and using your birthday or anniversary is not safe . but after that , he learned another trick . and he got the number down to 20 . out of all these million , there were 20 . and it turns out that if you open the safe and leave it open , and there 's a little draw on the bottom . and he goes into somebody else 's office . he chats to them . and the safe is open . he fiddles with all the knobs . and after two years of practice , he got these two sorted out by fiddling around with the knobs when the safe was open in somebody else 's office . he 'd go back afterwards -- and they do n't realize he 's been doing this -- and writes down these two numbers in a little book and says such and such . so by the end of the war , he could go into anybody 's office . he 's got the last two numbers . there are 20 settings . it takes him a minute and a half to open the safe , or less . so he really has to spin it up . he has a reputation of safe cracking . and everybody thinks he knows how to use picks . but he 's just used human nature , the tolerance of all this , and deviousness , just to show how clever he was . he was doing it just to show how clever he was . he was obnoxious . he would like to be one up on everybody else . but there was a security problem there . and the guy who he shared a room with was the guy who gave the secrets of the bomb to the russians , which is klaus fuchs . he was a roomie of his . brady haran : but for all his showing off about safe breaking , it turns out the real spy was in the room with him . professor roger bowley : yes . but i do n't -- well , yes . when you look at this , now that we live in worlds where you have a little security code for everything , this seems unbelievably primitive -- phone hacking and everything else going on . but people were n't -- if you 're a scientist , you 're not really looking at the other guy next door and wondering whether he 's letting all your secrets out .

so now , if you go through all the combinations , you only have to do 3 , 8 , 13 and so on -- every fifth one -- to make sure you cover them all . now , there are only 20 settings for this , 20 for that , and 20 for that . so automatically , that 's gone down , oh , i ca n't do it .

how did richard feynman eventually get it down to 20 combinations ?

stretched across a tree-peppered expanse in southern africa lies the magnificent ruins of great zimbabwe , a medieval stone city of astounding wealth and prestige . located in the present-day country of zimbabwe , it 's the sight of the largest known settlement ruins in sub-saharan africa , second on the continent only to the pyramids of egypt . but the history of this city is shrouded in controversy , defined by decades of dispute about who built it and why . its name comes from the shona word madzimbabwe , meaning big house of stone for its unscalable stone walls that reach heights of nearly ten meters and run for a length of about 250 meters . for its grandeur and historical significance , it was named a unesco world heritage site in 1986 . back in the 14th and 15th centuries , it was a thriving city . spread across nearly eight square-kilometers , great zimbabwe was defined by three main areas : the hill complex , where the king lived ; the great enclosure , reserved for members of the royal family ; and the valley complex , where regular citizens lived . rulers were both powerful economic and religious leaders for the region . at its highest point , the city had a bustling urban population of 18,000 people and was one of the major african trade centers at the time . what enabled this growth was great zimbabwe 's influential role in an intercontinental trade network . connected to several key city-states along the east african swahili coast , it was part of the larger indian ocean trade routes . the city generated its riches by controlling the sources and trade of the most prized items : gold , ivory , and copper . with this mercantile power , it was able to extend its sphere of influence across continents , fostering a strong arab and indian trader presence throughout its zenith . archaeologists have since pieced together the details of this history through artifacts discovered on site . there were pottery shards and glassworks from asia , as well as coins minted in the coastal trading city of kilwa kisiwani over 1,500 miles away . they also found soapstone bird figures , which are thought to represent each of the city 's rulers , and young calf bones , only unearthed near the royal residence , show how the diet of the elite differed from the general population . these clues have also led to theories about the city 's decline . by the mid-15th century , the buildings at great zimbabwe were almost all that remained . archaeological evidence points to overcrowding and sanitation issues as the cause , compounded by soil depletion triggered by overuse . eventually , as crops withered and conditions in the city worsened , the population of great zimbabwe is thought to have dispersed and formed the nearby mutapa and torwa states . centuries later , a new phase of great zimbabwe 's influence began to play out in the political realm as people debated who had built the famous city of stone . during the european colonization of africa , racist colonial officials claimed the ruins could n't be of african origin . so , without a detailed written record on hand , they instead relied on myths to explain the magnificence of great zimbabwe . some claimed it proved the bible story of the queen of sheba who lived in a city of riches . others argued it was built by the ancient greeks . then , in the early 20th century after extensive excavation at the site , the archaeologist david randall-maciver presented clear evidence that great zimbabwe was built by indigenous peoples . yet , at the time , the country 's white minority colonial government sought to discredit this theory because it challenged the legitimacy of their rule . in fact , the government actively encouraged historians to produce accounts that disputed the city 's african origins . over time , however , an overwhelming body of evidence mounted , identifying great zimbabwe as an african city built by africans . during the 1960s and 70s , great zimbabwe became an important symbol for the african nationalist movement that was spreading across the continent . today , the ruins at great zimbabwe , alluded to on the zimbabwean flag by a soapstone bird , still stand as a source of national pride and cultural value .

at its highest point , the city had a bustling urban population of 18,000 people and was one of the major african trade centers at the time . what enabled this growth was great zimbabwe 's influential role in an intercontinental trade network . connected to several key city-states along the east african swahili coast , it was part of the larger indian ocean trade routes .

what evidence from archeologists indicates great zimbabwe was part of an intercontinental trade network ?

a banker in london sends the latest stock info to his colleagues in hong kong in less than a second . with a single click , a customer in new york orders electronics made in beijing , transported across the ocean within days by cargo plane or container ship . the speed and volume at which goods and information move across the world today is unprecedented in history . but global exchange itself is older than we think , reaching back over 2,000 years along a 5,000 mile stretch known as the silk road . the silk road was n't actually a single road , but a network of multiple routes that gradually emerged over centuries , connecting to various settlements and to each other thread by thread . the first agricultural civilizations were isolated places in fertile river valleys , their travel impeded by surrounding geography and fear of the unknown . but as they grew , they found that the arid deserts and steps on their borders were inhabited , not by the demons of folklore , but nomadic tribes on horseback . the scythians , who ranged from hungary to mongolia , had come in contact with the civilizations of greece , egypt , india and china . these encounters were often less than peaceful . but even through raids and warfare , as well as trade and protection of traveling merchants in exchange for tariffs , the nomads began to spread goods , ideas and technologies between cultures with no direct contact . one of the most important strands of this growing web was the persian royal road , completed by darius the first in the 5th century bce . stretching nearly 2,000 miles from the tigris river to the aegean sea , its regular relay points allowed goods and messages to travel at nearly 1/10 the time it would take a single traveler . with alexander the great 's conquest of persia , and expansion into central asia through capturing cities like samarkand , and establishing new ones like alexandria eschate , the network of greek , egyptian , persian and indian culture and trade extended farther east than ever before , laying the foundations for a bridge between china and the west . this was realized in the 2nd century bce , when an ambassador named zhang qian , sent to negotiate with nomads in the west , returned to the han emperor with tales of sophisticated civilizations , prosperous trade and exotic goods beyond the western borders . ambassadors and merchants were sent towards persia and india to trade silk and jade for horses and cotton , along with armies to secure their passage . eastern and western routes gradually linked together into an integrated system spanning eurasia , enabling cultural and commercial exhange farther than ever before . chinese goods made their way to rome , causing an outflow of gold that led to a ban on silk , while roman glassware was highly prized in china . military expeditions in central asia also saw encounters between chinese and roman soldiers . possibly even transmitting crossbow technology to the western world . demand for exotic and foreign goods and the profits they brought , kept the strands of the silk road in tact , even as the roman empire disintegrated and chinese dynasties rose and fell . even mongolian hoards , known for pillage and plunder , actively protected the trade routes , rather than disrupting them . but along with commodities , these routes also enabled the movement of traditions , innovations , ideologies and languages . originating in india , buddhism migrated to china and japan to become the dominant religion there . islam spread from the arabian penninsula into south asia , blending with native beliefs and leading to new faiths , like sikhism . and gunpowder made its way from china to the middle east forging the futures of the ottoman , safavid and mughul empires . in a way , the silk road 's success led to its own demise as new maritime technologies , like the magnetic compass , found their way to europe , making long land routes obsolete . meanwhile , the collapse of mongol rule was followed by china 's withdrawal from international trade . but even though the old routes and networks did not last , they had changed the world forever and there was no going back . europeans seeking new maritime routes to the riches they knew awaited in east asia led to the age of exploration and expansion into africa and the americas . today , global interconnectedness shapes our lives like never before . canadian shoppers buy t-shirts made in bangladesh , japanese audiences watch british television shows , and tunisians use american software to launch a revolution . the impact of globalization on culture and economy is indisputable . but whatever its benefits and drawbacks , it is far from a new phenomenon . and though the mountains , deserts and oceans that once separated us are now circumvented through super sonic vehicles , cross-continental communication cables , and signals beamed through space rather than caravans traveling for months , none of it would have been possible without the pioneering cultures whose efforts created the silk road : history 's first world wide web .

the speed and volume at which goods and information move across the world today is unprecedented in history . but global exchange itself is older than we think , reaching back over 2,000 years along a 5,000 mile stretch known as the silk road . the silk road was n't actually a single road , but a network of multiple routes that gradually emerged over centuries , connecting to various settlements and to each other thread by thread . the first agricultural civilizations were isolated places in fertile river valleys , their travel impeded by surrounding geography and fear of the unknown .

what role did nomadic people play in the establishment of the silk road trade ?

all animals communicate . crabs wave their claws at each other to signal that they 're healthy and ready to mate . cuttlefish use pigmented skin cells called chromatophores to create patterns on their skin that act as camouflage or warnings to rivals . honeybees perform complex dances to let other bees know the location and quality of a food source . all of these animals have impressive communication systems , but do they have language ? to answer that question , we can look at four specific qualities that are often associated with language : discreteness , grammar , productivity , and displacement . discreteness means that there is a set of individual units , such as sounds or words , that can be combined to communicate new ideas , like a set of refrigerator poetry magnets you can rearrange to create different phrases . grammar provides a system of rules that tells you how to combine those individual units . productivity is the ability to use language to create an infinite number of messages . and displacement is the ability to talk about things that are n't right in front of you , such as past , future , or fictional events . so , does animal communication exhibit any of these qualities ? for crabs and cuttlefish , the answer is no . they do n't combine their signals in creative ways . those signals also do n't have to be in a grammatical order , and they only communicate current conditions , like , `` i am healthy , '' or `` i am poisonous . '' but some animals actually do display some of these properties . bees use the moves , angle , duration , and intensity of their waggle dance to describe the location and richness of a food source . that source is outside the hive , so they exhibit the property of displacement . they share that language trait with prairie dogs , which live in towns of thousands , and are hunted by coyotes , hawks , badgers , snakes , and humans . their alarms calls indicate the predator 's size , shape , speed , and , even for human predators , what the person is wearing and if he 's carrying a gun . great apes , like chimps and gorillas , are great communicators , too . some have even learned a modified sign language . a chimpanzee named washoe demonstrated discreteness by combining multiple signs into original phrases , like , `` please open . hurry . '' coco , a female gorilla who understands more than 1000 signs , and around 2000 words of spoken english referred to a beloved kitten that had died . in doing so , she displayed displacement , though it 's worth noting that the apes in both of these examples were using a human communication system , not one that appeared naturally in the wild . there are many other examples of sophisticated animal communication , such as in dolphins , which use whistles to identify age , location , names , and gender . they can also understand some grammar in a gestural language researchers use to communicate with them . however , grammar is not seen in the dolphin 's natural communication . while these communication systems may have some of the qualities of language we 've identified , none display all four . even washoe and coco 's impressive abilities are still outpaced by the language skills of most three-year-old humans . and animals ' topics of conversation are usually limited . bees talk about food , prairie dogs talk about predators , and crabs talk about themselves . human language stands alone due to the powerful combination of grammar and productivity , on top of discreteness and displacement . the human brain can take a finite number of elements and create an infinite number of messages . we can craft and understand complex sentences , as well as words that have never been spoken before . we can use language to communicate about an endless range of subjects , talk about imaginary things , and even lie . research continues to reveal more and more about animal communication . it may turn out that human language and animal communication are n't entirely different but exist on a continuum . after all , we are all animals .

grammar provides a system of rules that tells you how to combine those individual units . productivity is the ability to use language to create an infinite number of messages . and displacement is the ability to talk about things that are n't right in front of you , such as past , future , or fictional events .

`` productivity '' refers to :

each year in the united states , players of sports and recreational activities receive between 2.5 and 4 million concussions . how dangerous are all those concussions ? the answer is complicated , and lies in how the brain responds when something strikes it . the brain is made of soft fatty tissue , with a consistency something like jello . inside its protective membranes and the skull 's hard casing , this delicate organ is usually well-shielded . but a sudden jolt can make the brain shift and bump against the skull 's hard interior , and unlike jello , the brain 's tissue is n't uniform . it 's made of a vast network of 90 billion neurons , which relay signals through their long axons to communicate throughout the brain and control our bodies . this spindly structure makes them very fragile so that when impacted , neurons will stretch and even tear . that not only disrupts their ability to communicate but as destroyed axons begin to degenerate , they also release toxins causing the death of other neurons , too . this combination of events causes a concussion . the damage can manifest in many different ways including blackout , headache , blurry vision , balance problems , altered mood and behavior , problems with memory , thinking , and sleeping , and the onset of anxiety and depression . every brain is different , which explains why people 's experiences of concussions vary so widely . luckily , the majority of concussions fully heal and symptoms disappear within a matter of days or weeks . lots of rest and a gradual return to activity allows the brain to heal itself . on the subject of rest , many people have heard that you 're not supposed to sleep shortly after receiving a concussion because you might slip into a coma . that 's a myth . so long as doctors are n't concerned there may also be a more severe brain injury , like a brain bleed , there 's no documented problem with going to sleep after a concussion . sometimes , victims of concussion can experience something called post-concussion syndrome , or pcs . people with pcs may experience constant headaches , learning difficulties , and behavioral symptoms that even affect their personal relationships for months or years after the injury . trying to play through a concussion , even for only a few minutes , or returning to sports too soon after a concussion , makes it more likely to develop pcs . in some cases , a concussion can be hard to diagnose because the symptoms unfold slowly over time . that 's often true of subconcussive impacts which result from lower impact jolts to the head than those that cause concussions . this category of injury does n't cause noticable symptoms right away , but can lead to severe degenerative brain diseases over time if it happens repeatedly . take soccer players , who are known for repeatedly heading soccer balls . using a technique called diffusion tensor imaging , we 're beginning to find out what effect that has on the brain . this method allows scientists to find large axon bundles and see how milder blows might alter them structurally . in 2013 , researchers using this technique discovered that athletes who had headed the ball most , about 1,800 times a year , had damaged the structural integrity of their axon bundles . the damage was similar to how a rope will fail when the individual fibers start to fray . those players also performed worse on short-term memory tests , so even though no one suffered full-blown concussions , these subconcussive hits added up to measurable damage over time . in fact , researchers know that an overload of subconcussive hits is linked to a degenerative brain disease known as chronic traumatic encephalopathy , or cte . people with cte suffer from changes in their mood and behavior that begin appearing in their 30s or 40s followed by problems with thinking and memory that can , in some cases , even result in dementia . the culprit is a protein called tau . usually , tau proteins support tiny tubes inside our axons called microtubules . it 's thought that repeated subconcussive hits damage the microtubules , causing the tau proteins to dislodge and clump together . the clumps disrupt transport and communication along the neuron and drive the breakdown of connections within the brain . once the tau proteins start clumping together , they cause more clumps to form and continue to spread throughout the brain , even after head impacts have stopped . the data show that at least among football players , between 50 and 80 % of concussions go unreported and untreated . sometimes that 's because it 's hard to tell a concussion has occurred in the first place . but it 's also often due to pressure or a desire to keep going despite the fact that something 's wrong . this does n't just undermine recovery . it 's also dangerous . our brains are n't invincible . they still need us to shield them from harm and help them undo damage once it 's been done .

that 's often true of subconcussive impacts which result from lower impact jolts to the head than those that cause concussions . this category of injury does n't cause noticable symptoms right away , but can lead to severe degenerative brain diseases over time if it happens repeatedly . take soccer players , who are known for repeatedly heading soccer balls .

describe what specifically happens to neurons when the brain is suddenly jolted .

a banker in london sends the latest stock info to his colleagues in hong kong in less than a second . with a single click , a customer in new york orders electronics made in beijing , transported across the ocean within days by cargo plane or container ship . the speed and volume at which goods and information move across the world today is unprecedented in history . but global exchange itself is older than we think , reaching back over 2,000 years along a 5,000 mile stretch known as the silk road . the silk road was n't actually a single road , but a network of multiple routes that gradually emerged over centuries , connecting to various settlements and to each other thread by thread . the first agricultural civilizations were isolated places in fertile river valleys , their travel impeded by surrounding geography and fear of the unknown . but as they grew , they found that the arid deserts and steps on their borders were inhabited , not by the demons of folklore , but nomadic tribes on horseback . the scythians , who ranged from hungary to mongolia , had come in contact with the civilizations of greece , egypt , india and china . these encounters were often less than peaceful . but even through raids and warfare , as well as trade and protection of traveling merchants in exchange for tariffs , the nomads began to spread goods , ideas and technologies between cultures with no direct contact . one of the most important strands of this growing web was the persian royal road , completed by darius the first in the 5th century bce . stretching nearly 2,000 miles from the tigris river to the aegean sea , its regular relay points allowed goods and messages to travel at nearly 1/10 the time it would take a single traveler . with alexander the great 's conquest of persia , and expansion into central asia through capturing cities like samarkand , and establishing new ones like alexandria eschate , the network of greek , egyptian , persian and indian culture and trade extended farther east than ever before , laying the foundations for a bridge between china and the west . this was realized in the 2nd century bce , when an ambassador named zhang qian , sent to negotiate with nomads in the west , returned to the han emperor with tales of sophisticated civilizations , prosperous trade and exotic goods beyond the western borders . ambassadors and merchants were sent towards persia and india to trade silk and jade for horses and cotton , along with armies to secure their passage . eastern and western routes gradually linked together into an integrated system spanning eurasia , enabling cultural and commercial exhange farther than ever before . chinese goods made their way to rome , causing an outflow of gold that led to a ban on silk , while roman glassware was highly prized in china . military expeditions in central asia also saw encounters between chinese and roman soldiers . possibly even transmitting crossbow technology to the western world . demand for exotic and foreign goods and the profits they brought , kept the strands of the silk road in tact , even as the roman empire disintegrated and chinese dynasties rose and fell . even mongolian hoards , known for pillage and plunder , actively protected the trade routes , rather than disrupting them . but along with commodities , these routes also enabled the movement of traditions , innovations , ideologies and languages . originating in india , buddhism migrated to china and japan to become the dominant religion there . islam spread from the arabian penninsula into south asia , blending with native beliefs and leading to new faiths , like sikhism . and gunpowder made its way from china to the middle east forging the futures of the ottoman , safavid and mughul empires . in a way , the silk road 's success led to its own demise as new maritime technologies , like the magnetic compass , found their way to europe , making long land routes obsolete . meanwhile , the collapse of mongol rule was followed by china 's withdrawal from international trade . but even though the old routes and networks did not last , they had changed the world forever and there was no going back . europeans seeking new maritime routes to the riches they knew awaited in east asia led to the age of exploration and expansion into africa and the americas . today , global interconnectedness shapes our lives like never before . canadian shoppers buy t-shirts made in bangladesh , japanese audiences watch british television shows , and tunisians use american software to launch a revolution . the impact of globalization on culture and economy is indisputable . but whatever its benefits and drawbacks , it is far from a new phenomenon . and though the mountains , deserts and oceans that once separated us are now circumvented through super sonic vehicles , cross-continental communication cables , and signals beamed through space rather than caravans traveling for months , none of it would have been possible without the pioneering cultures whose efforts created the silk road : history 's first world wide web .

and gunpowder made its way from china to the middle east forging the futures of the ottoman , safavid and mughul empires . in a way , the silk road 's success led to its own demise as new maritime technologies , like the magnetic compass , found their way to europe , making long land routes obsolete . meanwhile , the collapse of mongol rule was followed by china 's withdrawal from international trade .

the diffusion of maritime technology , like the magnetic compass , led to which effect ?

translator : ido dekkers reviewer : ariana bleau lugo so what is gravity ? i bet most of you think it 's : `` what goes up , must come down ! '' is that right ? well , sorta , but not really . technically , the law of gravity is an equation . it is : f = g x m1 x m2 / r^2 , where g is the universal gravitational constant , m1 and m2 are the masses of the two objects , and r is the distance between them squared . that was easy , right ? probably not . what does this actually mean ? well it means that - well , everything is attracted to everything else . what i mean by that is if you have two objects , any two objects , they are attracted to each other . ok. let 's try and wrap our minds around this . what happens when you drop a rock off a cliff ? it falls to the earth . right ? well , yes , but something else happens . you see , the law of gravity says that both objects , the rock and the earth , are attracted to each other . this means that the rock falls towards the earth , and the earth falls towards the rock . wait a second - you mean to tell me that if - the earth falls up to meet the rock ? yes , that 's exactly what i 'm saying . and the reason you do n't see the earth fall up to meet the rock is because the objects move towards each other proportionate to their respective masses . the earth is much much much more massive than the rock , so it moves a very very small distance , and the rock is much less massive , so it moves farther with respect to the earth . maybe a better way to understand gravity is to take two teenagers in spacesuits , and place them far out in space - away from all the planets and the stars . it turns out they will be attracted to each other . i 'm not talking about that kind of attraction . see , they have mass , and since they have mass , they will move towards each other . they are attracted to each other . maybe one more thing might help . have you ever played with two magnets ? you know , the magnets with the north and the south poles ? when you take the magnets and put them closer to each other , they move together . they are attracted to each other . and the closer they are , the stronger the attraction . think of the mass of the object like the strength of a magnet and the distance between the objects like the distance between the two magnets . now understand , i 'm not saying that gravity and magnetism are the same , they just behave in a similar way . let 's think of one other thing - astronauts . you know , astronauts , they weigh less on the moon than on the earth . why is that ? well you see , the moon is less massive than the earth . therefore it has a smaller gravitational pull on the astronaut . it 's like the moon is a weaker magnet . they are n't as attracted to each other . distance also plays a role . think back to playing with a magnet . the pull of the magnets towards each other are stronger when they are closer together . the same is true of gravity . for example , the sun is the most massive object near the earth . it dictates most of the gravitational forces in our solar system . it is very very massive . but it is relatively far away , so even though the sun is a much stronger magnet , so to speak , it is a long ways away . therefore the attraction is n't as strong . so let 's look back at that law of gravity . the equation : f = g x m1 x m2 / r ^2 . you see the force of gravity is equal to a number . that 's that universal gravitational constant g times the mass of object one , times the mass of object two . think of m1 being the mass of the sun and m2 being the mass of the earth . and then we divide by the distance between them squared . this determines the force of attraction between the sun and earth . you could just as easily plug in your mass and the earth 's mass and the distance between you and the center of the earth , and find out how much you are attracted to the earth , and the earth attracted to you . so , what 's gravity ? everything is attracted to everything else . everything . oh , one last thing , just to make you wonder . what causes gravity ? why are two objects with mass attracted to each other ? well , the answer is - we do n't know . the cause of gravity remains a mystery to scientists . we do n't really know conclusively what causes gravity . it is one of the great mysteries of science .

the earth is much much much more massive than the rock , so it moves a very very small distance , and the rock is much less massive , so it moves farther with respect to the earth . maybe a better way to understand gravity is to take two teenagers in spacesuits , and place them far out in space - away from all the planets and the stars . it turns out they will be attracted to each other .

if you place two teenagers with equal mass in space :

translator : andrea mcdonough reviewer : bedirhan cinar the universe , rather beautiful , is n't it ? it 's quite literally got everything , from the very big to the very small . sure , there are some less than savory elements in there , but on the whole , scholars agree that its existence is probably a good thing . such a good thing that an entire field of scientific endeavor is devoted to its study . this is known as cosmology . cosmologists look at what 's out there in space and piece together the tale of how our universe evolved : what it 's doing now , what it 's going to be doing , and how it all began in the first place . it was edwin hubble who first noticed that our universe is expanding , by noting that galaxies seem to be flying further and further apart . this implied that everything should have started with the monumental explosion of an infinitely hot , infinitely small point . this idea was jokingly referred to at the time as the `` big bang , '' but as the evidence piled up , the notion and the name actually stuck . we know that after the big bang , the universe cooled down to form the stars and galaxies that we see today . cosmologists have plenty of ideas about how this happened . but we can also probe the origins of the universe by recreating the hot , dense conditions that existed at the beginning of time in the laboratory . this is done by particle physicists . over the past century , particle physicists have been studying matter and forces at higher and higher energies . firstly with cosmic rays , and then with particle accelerators , machines that smash together subatomic particles at great energies . the greater the energy of the accelerator , the further back in time they can effectively peek . today , things are largely made up of atoms , but hundreds of seconds after the big bang , it was too hot for electrons to join atomic nuclei to make atoms . instead , the universe consisted of a swirling sea of subatomic matter . a few seconds after the big bang , it was hotter still , hot enough to overpower the forces that usually hold protons and neutrons together in atomic nuclei . further back , microseconds after the big bang , and the protons and neutrons were only just beginning to form from quarks , one of the fundamental building blocks of the standard model of particle physics . further back still , and the energy was too great even for the quarks to stick together . physicists hope that by going to even greater energies , they can see back to a time when all the forces were one and the same , which would make understanding the origins of the universe a lot easier . to do that , they 'll not only need to build bigger colliders , but also work hard to combine our knowledge of the very , very big with the very , very small and share these fascinating insights with each other and with , well , you . and that 's how it should be ! because , after all , when it comes to our universe , we 're all in this one together .

further back still , and the energy was too great even for the quarks to stick together . physicists hope that by going to even greater energies , they can see back to a time when all the forces were one and the same , which would make understanding the origins of the universe a lot easier . to do that , they 'll not only need to build bigger colliders , but also work hard to combine our knowledge of the very , very big with the very , very small and share these fascinating insights with each other and with , well , you .

unsurprisingly , there ’ s actually a lot more to the story of our universe than we could fit into this video . which particles are missing ? where do they fit into the story ? how might the story be different if we weren ’ t looking backwards in time ?

translator : andrea mcdonough reviewer : jessica ruby in the 11th and 12th centuries , most english commoners were illiterate . since they had no way to learn the bible , the clergy came up with an inventive solution : they 'd create plays out of certain bible stories so even people who could n't read could learn them . these were called mystery plays because they revealed the mystery of god 's word . at about the same time , the clergy also developed plays about the saints of the church , called miracle plays . in the beginning , the clergy members acted out bible stories on the steps outside the cathedral . the audience reacted so well that soon they needed to move out to the street around the town square . by building moving carts to put on each play and by lining up one after the other , they could put on cycles of stories , which would take the viewer from genesis to revelation . these movable carts , called pageants , looked like huge boxes on wheels . each was two stories tall . the bottom story was curtained off and was used for costumes , props , and dressing . the top platform was the stage for the performance . spectators assembled in various corners of the town , and the pageant would move around in the cycle until the villagers had seen the entire series . soon , the plays required more actors than the clergy could supply . so , by the 13th century , different guilds were asked to be responsible for acting out different parts of the cycle . the assignments were meant to reflect the guilds ' professions . for example , the carpenter 's guild might put on the story of noah 's ark , and the baker 's guild might put on the last supper . can you imagine what might happen to the story if the butcher 's guild put on the crucifixion of christ ? yes , without the clergy , the plays soon started changing from their true bible stories . by the end of the 14th century , a new form of drama , called the morality play , had evolved . faith , truth , charity , and good deeds all became characters on the stage . and , at the same time , the opposite virtues of falsehood , covetousness , worldly flesh , and the devil became the antagonists . the morality plays were allegorical stories in which these characters battled for the control of the soul . audiences loved the immoral characters , and spectators were encouraged to interact with the actors . throwing rotten food and even getting into scuffles with other spectators became very common . the character of the devil often would roam through the crowds and pull unsuspecting watchers into a hell that was depicted as a dragon 's mouth . the virtuous biblical stories had morphed into crude and sometimes comic stories . the clergy intended to teach against immorality . how ironic , then , that the morality plays actually encouraged vices as more popular than virtues . by the mid-15th century , the church started to outlaw these performances . town charters required that any theater must be built outside the city wall . one of the first theaters was built like a larger version of a pageant , with tiers of gallery seating encircling a grassy area in front of the stage . sound familiar ? a young william shakespeare developed his craft here at the theater that was eventually renamed the globe . the medieval morality play had led to renaissance playwrights who were inspired by the inner struggles and the conscience of man . and that , in essence , is how drama emerged as a literary art form .

the character of the devil often would roam through the crowds and pull unsuspecting watchers into a hell that was depicted as a dragon 's mouth . the virtuous biblical stories had morphed into crude and sometimes comic stories . the clergy intended to teach against immorality .

why do you think the plays deteriorated from holy stories to immoral productions ?

the evolutionary tango of animal genitalia . can you guess what you 're looking at ? if you answered `` duck vagina , '' you 'd be right . although the bird 's outward appearance may not strike you as especially odd , it uses this strange , intricate , cork-screw shaped contraption to reproduce . we see similarly unbelievable genitalia in insects , mammals , reptiles , fish , spiders , and even snails . apparently , no organs evolve faster and into more variable shapes than those involved in procreation . superficially , it makes sense because evolution works via reproduction . when an animal leaves more offspring , its genes will spread . and since genitalia are an animal 's tools for reproduction , any improvement there will have immediate effect . and yet , what 's the point of having such decorative nether regions ? after all , the function of genitalia seems simple . a penis deposits a bit of sperm and a vagina receives it and delivers it to the egg . a pipette-like thingy on the male and a funnel-like gizmo on the female should do just fine for any animal . and yet , that 's not what we see . the penis of a chicken flea , for example , looks nothing like a pipette , more like an exploded grandfather clock . and the vagina of a featherwing beetle resembles something you 'd find in a dr. seuss book . throughout the animal kingdom , genitalia are very complex things , much more complicated than seems necessary for what they 're meant to do . that 's because genitalia do more than just deposit and receive sperm . many male animals also use the penis as courtship device , like crane flies . in some south american species , males have a tiny washboard and scraper on their penis , which produces a song that reverberates throughout the female 's body when they mate . it 's thought that if female crane flies enjoy this unusual serenade , they 'll allow the male to father their offspring . this way , the genes of the most musical penises spread , leading to rapid evolution of insects ' phalluses . similarly , some beetles have two little drumsticks on either side of the penis . during mating , they 'll rub , slap , or tap the female with these . and some hoofed mammals , like rams and bulls , use a whip-like extension on the penis 's left side to create a sensation during mating . but how can females really choose between males if she can only assess them after mating ? this is where the power of female adaptation comes into play . in fact , insemination is different to conception , and the female genitalia exploit this distinction . for instance , in some dung flies , the vagina contains pockets for separating sperm from different males depending on how appealing they were . males using their penises for courtship and females controlling their own sperm management are two reasons why genitalia evolve into such complex shapes . but there are others because genitalia are also where a sexual conflict is played out . a female 's interests are best served if she fertilizes her eggs with the sperm of the best fathers and creates genetic variability amongst her offspring . for a male , on the other hand , this is bad news . for him , it would be best if a female used his sperm to fertilize all of her eggs . so we see cycles of adaptation in an evolutionary arms race to retain control . black widow spiders have a disposable penis tip that breaks off inside the vagina blocking the attempts of his rivals , and bed bug males bypass a female 's genitalia altogether using a syringe-like penis to inject sperm cells directly into her belly . not to be outdone , females have evolved their own countermeasures . in some bed bug species , the females have evolved an entirely new set of genitalia on their right hand flanks where the males usually pierce them . that allows them to maintain the power to filter out unwanted sperm with their genitalia . and duck vaginas are shaped like a clockwise spiral so that when the male inflates his long , counterclockwise coiled penis into her , and she disapproves , all she needs to do is flex her vaginal muscles and the penis just flubs out . so , genitalia differs so much , not just to fascinate us , but because in every species , they 're the result of a furious evolutionary tango of sex that has been going on for millions of years and will continue for millions of years to come .

not to be outdone , females have evolved their own countermeasures . in some bed bug species , the females have evolved an entirely new set of genitalia on their right hand flanks where the males usually pierce them . that allows them to maintain the power to filter out unwanted sperm with their genitalia .

why are genitals so useful for identifying species that otherwise look alike ?

translator : andrea mcdonough reviewer : bedirhan cinar coral reefs are some of the most spectacular ecosystems on the planet . they 're also some of the most vulnerable . but how can we protect the reefs and the animals and plants who rely on them ? and how can we make sure our protected areas are n't hurting those who use reefs to survive ? these are some of the big questions facing marine conservation biologists today . let 's take fiji , for example . fiji is series of islands in the south pacific ocean . to help balance the need for conservation and making a living , scientists had suggested that instead of one big park which provides a lot of coverage for one reef system while leaving the rest unprotected , a better way is to create a system of protected areas nested together like pearls on a string . this idea is called connectivity . in this way , scientists can protect lots of different habitats while not excluding people from their traditional fishing grounds . now , the only way this string-of-pearls kind of reserve network is going to work is if each park is connected to other parks . there are two main benefits to this . first of all , insurance . if something bad happens to one park , say , an oil spill or coral bleaching , then because that park is part of a system , it can be reseeded from other parks that escaped the event . the second benefit is representation . by conserving many different areas , scientists ensure that lots of different habitats get protected . this way , they can make sure all the different marine habitats in fiji , such as coral reefs , mangroves , and sea-grass beds , are all represented . this way , we do n't unduly settle any particular village or group of people with the economic burden of having their fishing grounds off-limits . by sharing the cost around the communities , they can also share the benefits . so if we agree that rather than one big park , we should have lots of parks of different sizes and covering different habitats , then scientists need to make sure those smaller parks are connected , because if they 're not , they probably wo n't be self-sustaining . but how do we know that ? that 's where genetics and dna come in . by looking at how closely related the fish in each one of these small reserves in fiji are to each other , scientists can figure out how much migration is going on among the reserves within the system . now it 's important to look at a variety of different species because there 's no guarantee that what 's going on with these guys is what 's going on with these guys . but if we look closely and at enough species , we can see whether or not the necklace is working . what scientists have found so far is that , in general , there 's a fair amount of connectivity amongst the parks within fiji . but it 's not just a big free-for-all ; rather , it seems that , for some species , babies born in the far west are having a hard time making it to the islands in the far east . to help deal with that , conservation biologists are suggesting that there be enough parks in both the east and the west to keep the populations healthy . this is n't just in fiji , either . lessons about reserve connectivity can help across the world . in places like indonesia , papua new guinea and the bahamas , scientists are using a variety of tools to help understand how individual parks can function together , so that their sum is greater than their whole . and this way , we can keep the beautiful necklace that is our coral reefs , intact .

but if we look closely and at enough species , we can see whether or not the necklace is working . what scientists have found so far is that , in general , there 's a fair amount of connectivity amongst the parks within fiji . but it 's not just a big free-for-all ; rather , it seems that , for some species , babies born in the far west are having a hard time making it to the islands in the far east . to help deal with that , conservation biologists are suggesting that there be enough parks in both the east and the west to keep the populations healthy .

scientists may notice a problem among fish born in a far western portion of a series of coral reefs . if the problem is successfully swimming to the far eat side of the corals , what might a conservation scientist suggest ?

as we walk through our daily environments , we 're surrounded by exotic creatures that are too small to see with the naked eye . we usually imagine these microscopic organisms , or microbes , as asocial cells that float around by themselves . but in reality , microbes gather by the millions to form vast communities known as biofilms . natural biofilms are like miniature jungles filled with many kinds of microbes from across the web of life . bacteria and archaea mingle with other microbes like algae , fungi , and protozoa , forming dense , organized structures that grow on almost any surface . when you pad across a river bottom , touch the rind of an aged cheese , tend your garden soil , or brush your teeth , you 're coming into contact with these invisible ecosystems . to see how biofilms come about , let 's watch one as it develops on a submerged river rock . this type of biofilm might begin with a few bacteria swimming through their liquid environment . the cells use rotating flagella to propel towards the surface of the rock , which they attach to with the help of sticky appendages . then , they start producing an extracellular matrix that holds them together as they divide and reproduce . before long , microcolonies arise , clusters of cells sheathed in this slimy , glue-like material . microcolonies grow to become towers , while water channels flow around them , functioning like a basic circulatory system . but why do microbes build such complex communities when they could live alone ? for one thing , microbes living in a biofilm are rooted in a relatively stable microenvironment where they may have access to a nutrient source . there 's also safety in numbers . out in the deep , dark wilderness of the microbial world , isolated microbes face serious risks . predators want to eat them , immune systems seek to destroy them , and there are physical dangers , too , like running out of water and drying up . however , in a biofilm , the extracellular matrix shields microbes from external threats . biofilms also enable interactions between individual cells . when microbes are packed against each other in close proximity , they can communicate , exchange genetic information , and engage in cooperative and competitive social behaviors . take the soil in your garden , home to thousands of bacterial species . as one species colonizes a plant root , its individual cells might differentiate into various subpopulations , each carrying out a specific task . matrix producers pump out the extracellular goo , swimmers assemble flagella and are free to move about or migrate , and spore-formers produce dormant , tough endospores that survive starvation , temperature extremes , and harmful radiation . this phenomenon is called division of labor . ultimately , it gives rise to a sophisticated system of cooperation that 's somewhat like a multicellular organism in itself . but because biofilms often contain many different microbes that are n't closely related to each other , interactions can also be competitive . bacteria launch vicious attacks on their competitors by secreting chemicals into the environment , or by deploying molecular spears to inject nearby cells with toxins that literally blow them up . in the end , competition is all about resources . if one species eliminates another , it keeps more space and food for itself . although this dramatic life cycle occurs beyond the limits of our vision , microbial communities provide humans and other species with tangible , and sometimes even delicious , benefits . microbes make up a major fraction of the biomass on earth and play a critical role within the global ecosystem that supports all larger organisms , including us . they produce much of the oxygen we breath , and are recruited to clean up environmental pollution , like oil spills , or to treat our waste water . not to mention , biofilms are normal and flavor enhancing parts of many of the foods we enjoy , including cheese , salami , and kombucha . so the next time you brush your teeth , bite into that cheese rind , sift through garden soil , or skip a river stone , look as close as you can . imagine the microbial jungles all around you waiting to be discovered and explored .

in the end , competition is all about resources . if one species eliminates another , it keeps more space and food for itself . although this dramatic life cycle occurs beyond the limits of our vision , microbial communities provide humans and other species with tangible , and sometimes even delicious , benefits . microbes make up a major fraction of the biomass on earth and play a critical role within the global ecosystem that supports all larger organisms , including us .

at the same time that cooperation occurs in a biofilm , fierce competition arises between different microbial species . why might one species act to eliminate another species in a biofilm , and how do microbes kill or slow the growth of competing species ?

the story of the buddha ’ s life , like all of buddhism , is a story about confronting suffering . he was born between the sixth and fourth century b.c. , the son of a wealthy king in the himalayan foothills of nepal . it was prophesied that the young buddha — then called siddhartha gautama — would either become the emperor of india or a very holy man . since siddhartha ’ s father desperately wanted him to become the former , he kept the child isolated in a palace . young gautama had every imaginable luxury : jewels , servants , lotus ponds , even beautiful dancing women . for 29 years , gautama lived in bliss , protected from the smallest misfortunes of the outside world but then , he left the palace for short excursions . what he saw amazed him : first he met a sick man , then an aging man , and then a dying man . show these kind of people in india—add them to the same image one by one he was astounded to discover that these unfortunate people represented normal—indeed , inevitable—parts of the human condition that would one day touch him , too . horrified and fascinated , gautama made a fourth trip outside the palace walls—and encountered a holy man , who had learned to seek spiritual life in the midst of the vastness of human suffering . inspired by the holy man , gautama left the palace for good . he tried to learn from other holy men . he almost starved himself to death by avoiding all physical comforts and pleasures , as they did . perhaps unsurprisingly , it did not bring him solace from suffering . then he thought of a moment when he was a small boy : sitting by the river , he ’ d noticed that when the grass was cut , the insects and their eggs were trampled and destroyed . as a child , he ’ d felt a deep compassion for the tiny insects . reflecting on his childhood compassion , gautama felt a profound sense of peace . he ate , meditated , and finally reached the highest state of enlightenment : nirvana it refers to the “ blowing out ” of the flames of desire . with this , gautama had become the buddha , “ the awakened one ” . the buddha awoke by recognising that all of creation , from distraught ants to dying human beings , is unified by suffering . recognising this , the buddha discovered how to best approach suffering . first , one shouldn ’ t bathe in luxury , nor abstain from food and comforts altogether . instead , one ought to live in moderation . the buddha called this the middle way this allows for maximal concentration on cultivating compassion for others and seeking enlightenment next , the buddha described a path to transcending suffering called the four noble truths the first noble truth is the realisation that first prompted the buddha ’ s journey : that there is suffering and constant dissatisfaction in the world . the second is that this suffering is caused by our desires . as the buddha said , “ attachment is the root of all suffering. ” the third truth is that we can transcend suffering by removing or managing these desires . the buddha thus made the remarkable claim that we must change our outlook , not our circumstances . we are unhappy not because we don ’ t have enough money , love or status but because we are greedy , vain , and insecure . by re-orienting our mind we can grow to be content . the people become happier—superimpose smiles or use a second image of their face with the correct behaviour and what we now term a mindful attitude , we can also become better people . we can invert negative emotions and states of mind , turning ignorance into wisdom , anger into compassion , and greed into generosity . the fourth and final noble truth the buddha uncovered is that we can learn to move beyond suffering through what he termed the noble eightfold path . the eightfold path involves a series of aspects of behaving “ right ” and wisely : right view , right intention , right speech , right action , right livelihood , right effort , right mindfulness , and right concentration . what strikes the western observer is the notion that wisdom is a habit , not merely an intellectual realisation . one must exercise one ’ s nobler impulses on a regular basis , as one would train a limb . the moment of understanding is only one part of becoming a better person . after his death , the buddha ’ s followers collected his “ sutras ” ( sermons or sayings ) into scripture , and developed texts to guide followers in meditation , ethics , and mindful living . the monasteries that had developed during the buddha ’ s lifetime grew and multiplied , throughout china and east asia . for a time , buddhism was particularly uncommon in india itself , and only a few quiet groups of yellow-clad monks and nuns roamed the countryside , meditating quietly in nature . but then , in the 3rd century b.c. , an indian king named ashoka grew troubled by the wars he had fought and converted to buddhism . he sent monks and nuns far and wide to spread the practice . buddhist spiritual tradition spread across asia and eventually throughout the world . buddha ’ s followers divided into two main schools : theravada buddhism which colonised southeast asia , and mahayana buddhism which took hold in china and northeast asia . today , there are between a half and one and a half billion buddhists in both east and west following the buddha ’ s teachings and seeking a more enlightened and compassionate state of mind . intriguingly , the buddha ’ s teachings are important regardless of our spiritual identification . like the buddha , we are all born into the world not realising how much suffering it contains , and unable to fully comprehend that misfortune , sickness , and death will come to us too . as we grow older , this reality often feels overwhelming , and we may seek to avoid it altogether . but the buddha ’ s teachings remind us of the importance of facing suffering directly . we must do our best to liberate ourselves from the grip of our own desires , and recognise that suffering can be viewed as part of our common connection with others , spurring us to compassion and gentleness .

the buddha awoke by recognising that all of creation , from distraught ants to dying human beings , is unified by suffering . recognising this , the buddha discovered how to best approach suffering . first , one shouldn ’ t bathe in luxury , nor abstain from food and comforts altogether .

according to the buddha , what happens when we see suffering as something that we have in common with all living things ?

aristotle famously said , `` nature fears of empty space '' when he claimed that a true vacuum , a space devoid of matter , could not exist because the surrounding matter would immediately fill it . fortunately , he turned out to be wrong . a vacuum is a key component of the barometer , an instrument for measuring air pressure . and because air pressure correlates to temperature and rapid shifts in it can contribute to hurricanes , tornadoes and other extreme weather events , a barometer is one of the most essential tools for weather forecasters and scientists alike . how does a barometer work , and how was it invented ? well , it took awhile . because the theory of aristotle and other ancient philosophers regarding the impossibility of a vacuum seemed to hold true in everyday life , few seriously thought to question it for nearly 2,000 years -- until necessity raised the issue . in the early 17th century , italian miners faced a serious problem when they found that their pumps could not raise water more than 10.3 meters high . some scientists at the time , including one galileo galilei , proposed that sucking air out of the pipe was what made water rise to replace the void . but that its force was limited and could lift no more than 10.3 meters of water . however , the idea of a vacuum existing at all was still considered controversial . and the excitement over galileo 's unorthodox theory , led gasparo berti to conduct a simple but brilliant experiment to demonstrate that it was possible . a long tube was filled with water and placed standing in a shallow pool with both ends plugged . the bottom end of the tube was then opened and water poured out into the basin until the level of the water remaining in the tube was 10.3 meters . with a gap remaining at the top , and no air having entered the tube , berti had succeeded in directly creating a stable vacuum . but even though the possibility of a vacuum had been demonstrated , not everyone was satisfied with galileo 's idea that this empty void was exerting some mysterious yet finite force on the water . evangelista torricelli , galileo 's young pupil and friend , decided to look at the problem from a different angle . instead of focusing on the empty space inside the tube , he asked himself , `` what else could be influencing the water ? '' because the only thing in contact with the water was the air surrounding the pool , he believed the pressure from this air could be the only thing preventing the water level in the tube from dropping further . he realized that the experiment was not only a tool to create a vacuum , but operated as a balance between the atmospheric pressure on the water outside the tube and the pressure from the water column inside the tube . the water level in the tube decreases until the two pressures are equal , which just happens to be when the water is at 10.3 meters . this idea was not easily accepted , as galileo and others had traditionally thought that atmospheric air has no weight and exerts no pressure . torricelli decided to repeat berti 's experiment with mercury instead of water . because mercury was denser , it fell farther than the water and the mercury column stood only about 76 centimeters tall . not only did this allow torricelli to make the instrument much more compact , it supported his idea that weight was the deciding factor . a variation on the experiment used two tubes with one having a large bubble at the top . if galileo 's interpretation had been correct , the bigger vacuum in the second tube should have exerted more suction and lifted the mercury higher . but the level in both tubes was the same . the ultimate support for torricelli 's theory came via blaise pascal who had such a mercury tube taken up a mountain and showed that the mercury level dropped as the atmospheric pressure decreased with altitude . mercury barometers based on torricelli 's original model remained one of the most common ways to measure atmospheric pressure until 2007 when restrictions on the use of mercury due to its toxicity led to them no longer being produced in europe . nevertheless , torricelli 's invention , born of the willingness to question long accepted dogmas about vacuums and the weight of air , is an outstanding example of how thinking outside of the box -- or the tube -- can have a heavy impact .

and because air pressure correlates to temperature and rapid shifts in it can contribute to hurricanes , tornadoes and other extreme weather events , a barometer is one of the most essential tools for weather forecasters and scientists alike . how does a barometer work , and how was it invented ? well , it took awhile .

explain why denser liquids work better in compact barometers .

translator : tom carter reviewer : bedirhan cinar every minute of every day , you breathe without even thinking about it . your body does it on its own , from the day you 're born until the day you die . you have muscles contract to bring oxygen , a gas , into your lungs , which is then transferred by your bloodstream to every cell in your body . gases are strange . we ca n't see them , but we know they 're there because we can feel them . what we experience as wind is really trillions and trillions of gas molecules slamming into your body . and it feels good , right ? science is based on observation . unfortunately , we can not observe gases with our eyes -- they 're too small . we have to use our other senses to make observations and draw conclusions . observations are then compiled , and we create a model . no , not that kind of model . a model is a way scientists describe the properties of physical phenomena . first , gases always move in a straight line . we do n't really have anything to demonstrate this with because gravity always pulls objects down . so imagine a bullet fired from a gun , and that bullet goes on at a constant speed in a perfectly straight line . that would be like a gas molecule . second , gases are so small , they occupy no volume on their own . as a group they do , blow up any balloon and you can see how that volume changes . but single gases have no volume compared to other forms of matter . rather than calculating such a small amount of matter , we just call it zero for simplicity . third , if gas molecules collide , and they do -- remember , these are assumptions -- their energy remains constant . an easy way to demonstrate this is by dropping a soccer ball with a tennis ball balanced on top . because the soccer ball is bigger , it has more potential energy , and the energy from the larger ball is transferred to the smaller tennis ball and it flies away when that energy is transferred . the total energy stays the same . gases work the same way . if they collide , smaller particles will speed up , larger particles will slow down . the total energy is constant . fourth , gases do not attract one another , and they do n't like to touch . but remember rule three . in reality , they do collide . finally , gases have energy that is proportional to the temperature . the higher the temperature , the higher the energy the gases have . the crazy thing is that at the same temperature , all gases have the same energy . it does n't depend on the type of gas , just the temperature that gas is at . keep in mind this is a model for the way gas particles behave , and based on our observations , gases always move in straight lines . they 're so small , that they 're not measurable on their own , and they do n't interact with one another . but if they do bump into one another , that energy is transferred from one particle to another , and the total amount never changes . temperature has a major effect , and in fact , all gases at the same temperature have the same average energy . whew ! i need to go catch my breath .

we have to use our other senses to make observations and draw conclusions . observations are then compiled , and we create a model . no , not that kind of model . a model is a way scientists describe the properties of physical phenomena .

what is a scientific model ?

you may think you know the words that sit plainly in black on your page , but do n't be fooled . some words are capable of taking on different guises , masquerading as nouns , verbs and adjectives that alter their meanings entirely . this seeming superpower is called lexical ambiguity . it can turn words and sentences into mazes that mess with our minds . for example , consider the following : buffalo buffalo buffalo buffalo buffalo buffalo buffalo buffalo . that may sound like nonsense , but it 's actually a grammatically correct sentence . how ? well , buffalo is proper noun , a noun , and a verb . it refers to an animal also known as a bison , an american city , and it can also mean to bully . these different interpretations create a sequence of words that is grammatically correct as it stands , though it helps to add in a few implied phrases and punctuation marks to reveal what 's really going on . buffalo buffalo are bison from the city of buffalo , and this sentence has three groups of them . group a , which is bullied by group b , bullies group c. in other words , bison from buffalo that other bison from buffalo bully also bully bison from buffalo . if you let each buffalo perform its role , the meaning becomes apparent . what if the bunch of bullying buffalo decides to cross the ocean ? not just on any ship , but a ship-shipping ship shipping shipping-ships ? that sentence sounds just as outrageous , but there 's logic to the babble . ship can mean a vessel and to transport . when we sub in those meanings , a clearer picture emerges . here we have a huge ship-carrying vessel transporting ships that themselves are designed to carry goods across the sea . a ship-shipping ship , shipping shipping-ships . how about some entertainment on board this unusual vessel to offset the scuffling buffalo ? consider the can-can . can-can can-can can can can can can-can . here , the word can comes in many guises . there 's can-can , the flamboyant dance , can , that means able to , and can , figuratively meaning to outperform . by sticking in a comma and including the implied meanings , this sentence becomes clearer . can-can dances that can-can dances are able to outperform , can also outperform other can-can dances . you would n't necessarily use any of these sentences in a conversation . they 're just too ridiculous . yet they serve as an extreme example on just how tangled everyday language can be . lexical ambiguities sail into our speech and writing all the time , spreading confusion and misunderstanding wherever they can-can .

you may think you know the words that sit plainly in black on your page , but do n't be fooled . some words are capable of taking on different guises , masquerading as nouns , verbs and adjectives that alter their meanings entirely . this seeming superpower is called lexical ambiguity .

here 's another one , except in this case the words are easier to tell apart because some of them are spelt differently . explain what you think this sentence means : `` rose rose to put rose roes on her rows of roses . ''

which of these entities has evolved the ability to manipulate an animal many times its size ? the answer is all of them . these are all parasites , organisms that live on or inside another host organism , which they harm and sometimes even kill . parasite survival depends on transmitting from one host to the next , sometimes through an intermediate species . our parasites elegantly achieve this by manipulating their host 's behavior , sometimes through direct brain hijacking . for example , this is the gordian worm . one of its hosts , this cricket . the gordian worm needs water to mate , but the cricket prefers dry land . so once it 's big enough to reproduce , the worm produces proteins that garble the cricket 's navigational system . the confused cricket jumps around erratically , moves closer to water , and eventually leaps in , often drowning in the process . the worm then wriggles out to mate and its eggs get eaten by little water insects that mature , colonize land , and are , in turn , eaten by new crickets . and thus , the gordian worm lives on . and here 's the rabies virus , another mind-altering parasite . this virus infects mammals , often dogs , and travels up the animal 's nerves to its brain where it causes inflammation that eventually kills the host . but before it does , it often increases its host 's aggressiveness and ramps up the production of rabies-transmitting saliva , while making it hard to swallow . these factors make the host more likely to bite another animal and more likely to pass the virus on when it does . and now , meet ophiocordyceps , also known as the zombie fungus . its host of choice is tropical ants that normally live in treetops . after ophiocordyceps spores pierce the ant 's exoskeleton , they set off convulsions that make the ant fall from the tree . the fungus changes the ant 's behavior , compelling it to wander mindlessly until it stumbles onto a plant leaf with the perfect fungal breeding conditions , which it latches onto . the ant then dies , and the fungus parasitizes its body to build a tall , thin stalk from its neck . within several weeks , the stalk shoots off spores , which turn more ants into six-legged leaf-seeking zombies . one of humanity 's most deadly assailants is a behavior-altering parasite , though if it 's any consolation , it 's not our brains that are being hijacked . i 'm talking about plasmodium , which causes malaria . this parasite needs mosquitoes to shuttle it between hosts , so it makes them bite more frequently and for longer . there 's also evidence that humans infected with malaria are more attractive to mosquitoes , which will bite them and transfer the parasite further . this multi-species system is so effective , that there are hundreds of millions of malaria cases every year . and finally , there are cats . do n't worry , there probably are n't any cats living in your body and controlling your thoughts . i mean , probably . but there is a microorganism called toxoplasma that needs both cats and rodents to complete its life cycle . when a rat gets infected by eating cat feces , the parasite changes chemical levels in the rat 's brain , making it less cautious around the hungry felines , maybe even attracted to them . this makes them easy prey , so these infected rodents get eaten and pass the parasite on . mind control successful . there 's even evidence that the parasite affects human behavior . in most cases , we do n't completely understand how these parasites manage their feats of behavior modification . but from what we do know , we can tell that they have a pretty diverse toolbox . gordian worms seem to affect crickets ' brains directly . the malaria parasite , on the other hand , blocks an enzyme that helps the mosquitoes feed , forcing them to bite over and over and over again . the rabies virus may cause that snarling , slobbering behavior by putting the immune system into overdrive . but whatever the method , when you think about how effectively these parasites control the behavior of their hosts , you may wonder how much of human behavior is actually parasites doing the talking . since more than half of the species on earth are parasites , it could be more than we think .

these are all parasites , organisms that live on or inside another host organism , which they harm and sometimes even kill . parasite survival depends on transmitting from one host to the next , sometimes through an intermediate species . our parasites elegantly achieve this by manipulating their host 's behavior , sometimes through direct brain hijacking .

toxoplasma is an example of a trophically transmitted parasite : a parasite that infects a definitive host ( a cat in the case of toxoplasma ) when that definitive host eats an intermediate host ( a rodent in the case of toxoplasma ) . another trophically transmitted parasite is the trematode flatworm leucochloridium paradoxum . this parasite infects the tentacles of snails , making them look like pulsating caterpillars . provide a hypothesis for this manipulation of the snail host .

for many of us , a typical day involves interactions with hundreds of companies . buying their goods , using their services , even wearing their names . corporations and companies have become such a familiar part of the modern landscape that it 's easy to forget they 're artificial entities created to allow real people to do business . but there are some types of companies that are n't engaged in any business at all . instead , these anonymous companies exist mainly to disguise people doing things they 'd rather not have the public know about . and these people go to great lengths to hide any links between their names and the companies they own . the life of an anonymous company usually begins in what 's known as a secrecy jurisdiction , a place whose laws allow new companies to be registered with little disclosure about who owns or controls them . some may simply not require collecting that information . others may collect it , but make it nearly inaccessible to anyone else . and the lack of incentive to verify companies ' real owners makes it easy for people to cover their tracks . for example , someone may register a company in the name of a relative , an associate , or even a nominee director who acts on instruction from the company 's actual owner while keeping their name confidential . once registered , a company can do many of the same things as a human being , like opening bank accounts , buying and owning assets , and transferring money . what 's more , it can be listed as the owner of other companies , including ones opened in places with stricter disclosure rules . this allows someone to create a complex world-wide chain of ownership that can take years to unravel . a company based in the u.s. may be wholly owned by another one in liechtenstein , which is owned in turn by one in the british virgin islands . and an anonymous company can be transferred to a new owner at any time with no public record of the change . so why all the anonymity ? defenders of financial secrecy argue that wealthy individuals need it to avoid intrusive media attention and threats to personal security . but while this may sometimes be justified , anonymous companies play a role in almost every type of economic crime , including many major corruption cases . they are used by corporations evading taxes , rogue governments skirting sanctions , terrorists buying arms , and dictators financing wars . organized crime groups launder their profits through anonymous companies . corrupt government officials award valuable contracts to corporations they secretly own . international oligarchs with criminal connections or questionable pasts have used anonymous companies to discretely buy luxury apartments in cities like london and new york city , keeping them as safe stores of wealth . and even when criminals are convicted , their anonymously held assets may be difficult for authorities to locate or seize , making it harder for victims to be compensated . efforts are now underway to chip away at these crime-enabling mechanisms . international authorities and ngos have called for requiring companies to state who ultimately makes their decisions and benefits from their assets . but while progress is being made , international cooperation has been difficult to achieve , as governments that profit from registering anonymous companies are reluctant to lose business . and some of the most popular places for this practice are located not on remote , tropical tax shelters , but within the same advanced nations which claim to be leading the fight for global financial transparency . but still , it 's a fight worth fighting . closing the legal loopholes that enable anonymous companies would help us cut down on corruption and illegal activity . it would also allow us , as the general public , to better understand the flow of enormous sums of money that impact politics , our daily lives , and the health of our world .

and the lack of incentive to verify companies ' real owners makes it easy for people to cover their tracks . for example , someone may register a company in the name of a relative , an associate , or even a nominee director who acts on instruction from the company 's actual owner while keeping their name confidential . once registered , a company can do many of the same things as a human being , like opening bank accounts , buying and owning assets , and transferring money .

what are some factors that make it possible to register an anonymous company ?

translator : andrea mcdonough reviewer : bedirhan cinar our earth is a collection of puzzle pieces that make up the universe . in the vast darkness of space , the universe is lit by stars , which could one day become a supernova and create all the puzzle pieces that we know today as the elements . all elements were formed and released into space by exploding stars . for centuries , humans have tried to discover what makes up the world around them . little did they know that all the pieces they needed were right under their noses . the discovery of these pieces revolutionized our understanding of the world and allowed for the creation of what might be the greatest gift to science : the periodic table . so , where are these elements , and how do we find a means to order them ? well , believe it or not , ancient civilizations were very much aware of many elements around them , but they did not identify them as the pieces of our universe . elements like gold , silver , and copper were easily spotted by ancient cultures , and were used for multiple purposes like jewelry and tools . why were these elements spotted so easily ? think of the periodic table as a puzzle . the corner pieces are edges of a puzzle , are generally the easiest to find and place because they stand out with their smooth edges , and clearly do n't interlock with other puzzle pieces . like puzzle pieces , elements can be choosy on who they interact with . some like to react with other elements , while others do not . the elements that do not interact with other elements are easy to pin-point , while the ones who like to interact with others are difficult to find . gold , silver , and copper are some of the choosier elements so we can find them easier . so let 's fast forward to the late 1600 's where hennig brand , a german alchemist , was busy working in his laboratory . like many other alchemists of his time , brand was trying to extract gold from the human body . brand hit upon what he thought was the most obvious answer to his problem : urine . urine is gold in coloration and could perhaps have gold in it . so , brand collected as much urine as he possibly could , much of it being his own , then he decided to boil it down in hopes of obtaining gold . so brand boiled his , well , urine , down until he collected a paste and heated the paste to a very high temperature . eventually smoke appeared and the material burned brightly and violently . brand had unknowingly isolated phosphorous from his urine . it was the first time anyone had discovered an element , but he did n't really understand what he had done . at the time of brand , the concept of element had not been discovered . instead ancient greek principles of objects being composed of earth , water , air , and fire were predominant . it was n't until the work of antoine lavoisier , who is now known as the father of chemistry , that science defined what an element was . lavoisier defined an element as a substance that can not be broken down by existing chemical means . lavoisier created a list of the known elements of his time and tried to put the elements in some sort of order in which they could be classified , such as gases or metals . he was the first one to try to put the puzzle together . this was just the beginning of a means to organize the known elements of his time . many other chemists then came along to make the puzzle clearer . one of them , john dalton , weighed the elements and arranged the puzzle by weight . german chemist wolfgang döbereiner later combined elements to see how they reacted with one another . what he found was that certain elements shared similar properties and reactions . for example , when pure lithium , sodium , and potassium are exposed to water , they will react violently and skid across the surface of the water with sparks . the scientists then realized that these similiarities are no coincidence : elements belong to families that share similar properties . but the chemist who finally put the puzzle together is dmitri mendeleev . he created cards of each known element and tried to order them based on atomic weight and their known properties . the story is that he stayed up 3 days and 3 nights , and he finally fell into a deep sleep and he dreamed about a table to order the elements . mendeleev was not only able to create the periodic table , but he was able to predict elements that were not yet discovered . the puzzle of the periodic table of the elements was solved .

what he found was that certain elements shared similar properties and reactions . for example , when pure lithium , sodium , and potassium are exposed to water , they will react violently and skid across the surface of the water with sparks . the scientists then realized that these similiarities are no coincidence : elements belong to families that share similar properties .

which element reacts violently with water ?

have you ever noticed that it 's harder to start pedaling your bicycle than it is to ride at a constant speed ? or wondered what causes your bicycle to move ? or thought about why it goes forward instead of backwards or sideways ? perhaps not , and you would n't be alone . it was n't until the 17th century that isaac newton described the fundamental laws of motion and we understood the answer to these three questions . what newton recognized was that things tend to keep on doing what they are already doing . so when your bicycle is stopped , it stays stopped , and when it is going , it stays going . objects in motion tend to stay in motion and objects at rest tend to stay at rest . that 's newton 's first law . physicists call it the law of inertia , which is a fancy way of saying that moving objects do n't spontaneously speed up , slow down , or change direction . it is this inertia that you must overcome to get your bicycle moving . now you know that you have to overcome inertia to get your bicycle moving , but what is it that allows you to overcome it ? well , the answer is explained by newton 's second law . in mathematical terms , newton 's second law says that force is the product of mass times acceleration . to cause an object to accelerate , or speed up , a force must be applied . the more force you apply , the quicker you accelerate . and the more mass your bicycle has , and the more mass you have too , the more force you have to use to accelerate at the same rate . this is why it would be really difficult to pedal a 10,000 pound bicycle . and it is this force , which is applied by your legs pushing down on the pedals , that allows you to overcome newton 's law of inertia . the harder you push down on the pedals , the bigger the force and the quicker you accelerate . now on to the final question : when you do get your bike moving , why does it go forward ? according to newton 's third law , for every action , there is an equal and opposite reaction . to understand this , think about what happens when you drop a bouncy ball . as the bouncy ball hits the floor , it causes a downward force on the floor . this is the action . the floor reacts by pushing on the ball with the same force , but in the opposite direction , upward , causing it to bounce back up to you . together , the floor and the ball form what 's called the action/reaction pair . when it comes to your bicycle , it is a little more complicated . as your bicycle wheels spin clockwise , the parts of each tire touching the ground push backwards against the earth : the actions . the ground pushes forward with the same force against each of your tires : the reactions . since you have two bicycle tires , each one forms an action/reaction pair with the ground . and since the earth is really , really , really big compared to your bicycle , it barely moves from the force caused by your bicycle tires pushing backwards , but you are propelled forward .

so when your bicycle is stopped , it stays stopped , and when it is going , it stays going . objects in motion tend to stay in motion and objects at rest tend to stay at rest . that 's newton 's first law .

newton ’ s second law is often described as f = ma but this is misleading and does not describe what happens when multiple forces act . for this reason , a more accurate description is that the sum of all the forces acting on a single object equals mass times acceleration ; or fnet = ma . forces which act in the same direction on a single object add together while forces which act in opposite directions subtract . explain why , if objects in motion stay in motion and objects at rest stay at rest as mentioned in the talk , your bicycle eventually comes to a stop when you stop pedaling . hint : which forces are responsible for stopping you ?

deep underground lies stores of once inaccessible natural gas . this gas was likely formed over millions of years as layers of decaying organisms were exposed to intense heat and pressure under the earth 's crust . there 's a technology called hydraulic fracturing , or fracking , that can extract this natural gas , potentially powering us for decades to come . so how does fracking work , and why it is a source of such heated controversy ? a fracking site can be anywhere with natural gas , from a remote desert to several hundred feet from your backyard . it starts out with a long vertical hole known as a wellbore drilled down through layers of sediment . when the well reaches 2500 - 3000 meters , it 's at its kickoff point where it can begin the process of horizontal drilling . it turns 90 degrees and extends horizontally for about 1.5 kilometers through a compressed black layer called the shale rock formation . a specialized perforating gun is then lowered and fired , creating a series of small , inch-long holes that burst through the well 's casing into the rock layer . about three to four months after the initial drilling , the well is ready for fracking to begin . fracking fluid is pumped down into the well at a pressure so high , it cracks the shale rock , creating fractures through which the trapped gas and oil can escape . the fluid itself is more than 90 % water . the rest is made up of concentrated chemical additives . these vary depending on the specific characteristics of the fracking site , but usually fall into three categories : acids for clearing debris and dissolving minerals , friction-reducing compounds to create a slippery form of water known as slickwater , and disinfectant to prevent bacteria growth . sand or clay is also mixed into the water to prop open the fissures so the gas and oil can keep leaking out , even after the pressure is released . it 's estimated that all of fracking 's intense pumping and flushing uses an average of 3-6 million gallons of water per well . that 's actually not a lot compared to agriculture , power plants , or even golf course maintenance , but it can have a notable impact on local water supply . and disposing of used fracking water is also an issue . along with the trapped gas that 's pumped up to the surface , millions of gallons of flow-back liquid come gushing up . this liquid containing contaminants like radioactive material , salts , heavy metals , and hydrocarbons , needs to be stored and disposed of . that 's usually done in pits on-site in deep wells or off-site at water treatment facilities . another option is to recycle the flow-back liquid , but the recycling process can actually increase levels of contamination since the water is more toxic with each use . wells are typically encased in steel and cement to prevent contaminants from leaking into groundwater . but any negligence or fracking-related accidents can have devastating effects . fracturing directly into underground water hazardous underground seepage and leakage , and inadequate treatment and disposal of highly-toxic waste water can potentially contaminate drinking water around a fracking site . there 's also concern about the threat of earthquakes and damaged infrastructure from pressure and waste water injection . links between fracking and increased seismic activity leave unresolved questions about long-term pressure imbalances that might be happening deep beneath our feet . fracking 's biggest controversy , though , is happening above the ground . the general consensus is that burning natural gas is better for the environment than burning coal since the gas collected from fracking emits only half the carbon dioxide as coal per unit of energy . the pollution caused by the fracking itself , though , is n't negligible . methane that leaks out during the drilling and pumping process is many times more potent than carbon dioxide as a greenhouse gas . some scientists argue that methane eventually dissipates , so has a relatively low long-term impact . but a greater question hangs in the air . does fracking take time , money , and research away from the development of cleaner renewable energy sources ? natural gas is non-renewable , and the short-run economic interests supporting fracking may fall short in the face of global climate change . experts are still examining fracking 's overarching effects . although modern fracking has been around since the 1940s , it 's boomed in the last few decades . as other sources of natural gas decrease , the costs of non-renewable energies rise , and cutting-edge technologies make it so accessible . but many countries and regions have already banned fracking in response to environmental concerns . it 's undeniable that fracking has reshaped the energy landscape around the world , but for what long-term benefit and at what cost ?

it starts out with a long vertical hole known as a wellbore drilled down through layers of sediment . when the well reaches 2500 - 3000 meters , it 's at its kickoff point where it can begin the process of horizontal drilling . it turns 90 degrees and extends horizontally for about 1.5 kilometers through a compressed black layer called the shale rock formation .

the point at which horizontal drilling begins is :

translator : andrea mcdonough reviewer : bedirhan cinar let me guess , you 've got facebook albums full of photos . you have photos on your computer desktop , on your mobile phone , on your bedroom wall . you see photos in magazines and newspapers , on the side of buses , and of course , in your family albums . we take photos for granted in a major way . but , creating a picture that looked exactly like the person or thing that you were photographing was n't always obvious . in fact , in the past , it was a big mystery . how could you , in essence , take your reflection in the mirror and freeze it in there ? in the 9th century , the arab scientist alhazen had come up with the idea of using the camera obscura , which was literally a dark room , or box , with a single , small hole in one side that let light through . this would project the image outside into the wall inside . during the renaissance , artists like leonardo davinci used this method to introduce 3-d scenes onto a flat plane so that they could copy things , like perspective , more easily . in 1724 , johann heinrich schultz discovered that exposing certain silver compounds to light altered their appearance and left marks wherever the light touched . essentially , schultz found a way to record the images that alhazen was able to project , but only for a little while . schultz 's images disappeared soon after he had made them . it was n't until 1839 that people figured out how to project images onto light-sensitive surfaces that would retain the image after exposure , and thus , photography was born . at that point , it was mostly two inventors who fought for the best way to make photos . one was british scientist henry fox talbot , whose calotype process used paper and allowed many copies to be made from a single negative . the other inventor , louis daguerre , was an artist and chemist in france . he developed something called a daguerreotype , which used a silvered plate and which produced a sharper image . but the daguerreotype could only make positive images so copies had to be made by taking another photo . in the end , the daguerreotype won out as the first commercially successful photographic process mostly because the government made it freely available to the public . so now that photography was available , getting a picture of yourself would be a snap , right ? well , not exactly ! this process still required a whole dark room at the location of the photograph , which was a big hassle . picture the early photographers lugging enormous trailers with all their equipment wherever they wanted to take a picture . not only that , but the early processes had extremely long exposure times . to get a good photo , you would have to stand perfectly still for up to two minutes ! this led to development of inventions like the head holder , a wire frame that would hide behind you while supporting your head . it 's also why you do n't see people smiling in early photographs . it 's not that life was that bad , it was just hard to keep a steady grin for more than a few seconds , so people opted for a straight-faced look . and then george eastman came along . eastman believed that everyone should have access to photography , and he spent many late nights mixing chemicals in his mother 's kitchen to try to achieve a dry plate photographic process . this would allow exposed negatives to be stored and developed later at a more convenient place instead of carting those dark rooms , necessary for wet plates , around . after starting a business , which initially made dry plates , eastman eventually discovered plastic roll film that would fit in hand-held , inexpensive cameras . these cameras sold by the millions under the tag line , `` you push the button , we do the rest . '' while eastman was largely responsible for making photography a universal pastime , even he could not have dreamed of the ways photography had since shaped the world . it 's now estimated that over 380 billion photographs are taken each year . that 's more photographs each day than were taken in the first hundred years after photography was invented . say cheese !

during the renaissance , artists like leonardo davinci used this method to introduce 3-d scenes onto a flat plane so that they could copy things , like perspective , more easily . in 1724 , johann heinrich schultz discovered that exposing certain silver compounds to light altered their appearance and left marks wherever the light touched . essentially , schultz found a way to record the images that alhazen was able to project , but only for a little while .

who discovered that exposing certain silver compounds to light altered their appearance ?

currently i think there are eight intelligences that i ’ m very confident about and a few more that i ’ ve bene thinking about . i ’ ll share that with our audience . the first two intelligences are the ones which iq tests and other kind of standardized tests valorize and as long as we know there are only two out of eight it ’ s perfectly fine to look at them . linguistic intelligence is how well you ’ re able to use language . it ’ s a kind of skill that poets have , other kinds of writers , journalists tend to have linguistic intelligence , orators . the second intelligence is logical mathematical intelligence . as the name implies logicians , mathematicians , scientists have that kind of intelligence . they ’ re able to do mathematical proofs . they ’ re able to do scientific reasoning and experimentation . and it ’ s great to have language and logical intelligence because most tests really focus on that . and if you do well in those tests as long as you stay in school you think you ’ re smart . but if you ever walk out into broadway or the highway or into the woods or into a farm you then find out that other intelligences are at least this important . so the third intelligence is musical intelligence and that ’ s the capacity to appreciate different kinds of musics , to produce the music by voice or by an instrument or to conduct music . and people say well music is a talent . it ’ s not an intelligence . and i say well why if you ’ re good with words is that an intelligence but if you ’ re good with tones and rhythms and timbres nobody ’ s ever given me a good answer which is why it makes sense to talk about musical intelligence . and at certain cultures over history musical intelligence has been very important . the fourth intelligence is spatial intelligence . that ’ s the intelligence which allows us to handle and work in space that ’ s close by . a chess player would have spatial intelligence . a surgeon would have spatial intelligence . but there ’ s another variety of spatial intelligence which we use for a much broader navigation . that ’ s what an airplane pilot or a sea captain would have . how do you find your way around large territory and large space . similarly with the fifth intelligence bodily kinesthetic intelligence it comes in two flavors . one flavor is the ability to use your whole body to solve problems or to make things . and athletes and dancers would have that kind of bodily kinesthetic intelligence . but another variety is being able to use your hands or other parts of your body to solve problems or make things . a craft person would have bodily kinesthetic intelligence even if they weren ’ t particularly a good athlete or dancer . the sixth intelligence and seventh intelligence have to do with human beings . interpersonal intelligence is how you understand other people , how you motivate them , how you lead them , how you work with them , how you cooperate with them . anybody at any workplace with other people needs interpersonal intelligence . leaders hopefully have a lot of interpersonal intelligence . but any intelligence can be used in a pernicious way so the salesman that sells you something you don ’ t want for a price you don ’ t want to pay , he or she has got interpersonal intelligence . it ’ s just not being used in a way that we might prefer . the seventh kind of intelligence is difficult to assess but it ’ s very important . it ’ s intrapersonal intelligence . it ’ s the understanding yourself . if we go back a way in history and prehistory knowledge of yourself probably wasn ’ t that important because people did what their parents or grandparents did whether they were hunters or fisherman or craftspeople . but nowadays especially in developed society people lead their own lives . we follow our own careers . we often switch careers . we don ’ t necessarily live at home as we get older . and if you don ’ t have a good understanding of yourself you are in big trouble . so that ’ s intrapersonal intelligence . the eighth intelligence which i added some years ago is the naturalist intelligence . and that ’ s the capacity to make important relevant discriminations in the world of nature between one plant and another , between one animal and another . it ’ s the intelligence of the naturalist , the intelligence of charles darwin . i missed it the first go around when i wrote about it but i tried to atone by adding it to my list . and by the way you might say well but nature isn ’ t so important anymore . but in fact everything we do in the commercial world uses our naturalist intelligence . why do i buy this jacket rather than another one ? this sweater rather than another one ? one hair style rather than another ? those all make just the naturalist intelligence because the brain is very adaptive . and when an old use of a brain center no longer is relevant it gets hijacked for something new . so we ’ re all using our naturalist intelligence even if we never walk out into the woods or into the savannah of east asia . the two other intelligences which i ’ m interested in , one of them is called the teaching or pedagogical intelligence . the intelligence which allows us to be able to teach successfully to other people . now you could have two people who have exactly the same expertise and knowledge in the field but one is a very good teacher and the other isn ’ t . that probably doesn ’ t surprise individuals so much . but what got me fascinated was as young as two or three kids already know how to teach . now what does that mean ? you show a child how to do something let ’ s say a three or four year old and then you ask the child to explain it to an older person or to a younger person . and even the three or four year old will explain it very differently to a young person , will go through details , point things and speak slowly . and with an older person it would be much more elliptical and say well you do this and that and then you can figure it out . so that shows as young as three let ’ s say we already have teaching intelligence . the other one is one which i think is going to be difficult to prove to a skeptic but i call it existential intelligence . and existential intelligence is the intelligence of big questions . philosophical questions , artistic questions . what does it mean to love ? why do we die ? what ’ s going to be in the future ? my pet bird might have more musical intelligence . the rats who are scurrying around the floor might have more spatial intelligence . but no other animals have existential intelligence . part of the human condition is to think about questions of existence . and i like to say every five year old has existential intelligence because five year old are always asking why this , why that . but the difference between a five year old and a philosopher is the five year old doesn ’ t pay too much attention to the answer whereas philosophers and other people who develop existential intelligence are really very interested in how we attack questions like that . so again where there ’ s eight intelligences or ten or twelve is less important to me than having broken the monopoly of a single intelligence which sort of labels you for all time . i think if we lived forever we could probably develop each intelligence to a very high degree . but life is very short and if you devote too much attention to one intelligence you ’ re not going to have much time to work on other kinds of intelligences . and so the big question is should you play to strength or should you bolster weakness ? and that ’ s a value judgment . scientists can not give you an answer to that . if , for example , you want to be a jack of all trades and be very well rounded then probably you ’ re going to want to nurture the intelligences which aren ’ t that strong . if on the other hand you ’ re dead set on really coming to the top of some particular heap then you ’ re probably going to find the intelligences that you ’ re strongest at and really push those . and , you know , if a parent came to me and said well should we supplement or should we accentuate i would say well tell me what you would like your child to do . or better let the child tell you what he or she wants to do rather than say well science says you should do one or the other . i think it ’ s a question of values , not of science . some people think there ’ s such a thing as humor intelligence . but , in fact , i don ’ t . i think humor intelligence is simply the operation of a logical intelligence in some realm like human nature or physical nature or the workplace . and what happens is in humor there ’ s a certain expectation and you flip that expectation so it ’ s logic but it ’ s logic that ’ s played out in different kinds of ways . people had mentioned there ’ s such a thing as a cooking intelligence , a humor intelligence and a sexual intelligence . and i quipped well that can ’ t be intelligences because i don ’ t have any of them .

the other one is one which i think is going to be difficult to prove to a skeptic but i call it existential intelligence . and existential intelligence is the intelligence of big questions . philosophical questions , artistic questions .

what is existential intelligence ?

in the summer of 1976 , a mysterious epidemic suddenly struck two central african towns , killing the majority of its victims . medical researchers suspected the deadly marburg virus to be the culprit . but what they saw in microscope images was an entirely new pathogen , which would be named after the nearby ebola river . like yellow fever or dengue , the disease caused by the ebola virus is a severe type of hemorrhagic fever . it begins by attacking the immune system 's cells and neutralizing its responses , allowing the virus to proliferate . starting anywhere from two to twenty days after contraction , initial symptoms like high temperature , aching , and sore throat resemble those of a typical flu , but quickly escalate to vomiting , rashes , and diarrhea . and as the virus spreads , it invades the lymph nodes and vital organs , such as kidneys and liver , causing them to lose function . but the virus itself is not what kills ebola victims . instead , the mounting cell deaths trigger an immune system overload , known as a cytokine storm , an explosion of immune responses that damages blood vessels , causing both internal and external bleeding . the excessive fluid loss and resulting complications can be fatal within six to sixteen days of the first symptoms , though proper care and rehydration therapy can significantly reduce mortality rates in patients . fortunately , while ebola is highly virulent , several factors limit its contagiousness . unlike viruses that proliferate through small , airborne particles , ebola only exists in bodily fluids , such as saliva , blood , mucus , vomit , or feces . in order to spread , these must be transmitted from an infected person into another 's body through passageways such as the eyes , mouth , or nose . and because the disease 's severity increases directly along with the viral load , even an infected person is unlikely to be contagious until they have begun to show symptoms . while ebola has been shown to survive on surfaces for several hours , and transmission through sneezing or coughing is theoretically possible , virtually all known cases of contraction have been through direct contact with the severely ill , with the greatest risk posed to medical workers and friends or relatives of the victims . this is why , despite its horrifying effects , ebola has been far less deadly overall than more common infections , such as measles , malaria , or even influenza . once an outbreak has been contained , the virus does not exist in the human population until the next outbreak begins . but while this is undoubtedly a good thing , it also makes ebola difficult to study . scientists believe fruit bats to be its natural carriers , but just how it is transmitted to humans remains unknown . furthermore , many of the countries where ebola outbreaks occur suffer from poor infrastructure and sanitation , which enables the disease to spread . and the poverty of these regions , combined with the relatively low amount of overall cases means there is little economic incentive for drug companies to invest in research . though some experimental medicines have shown promise , and governments are funding development of a vaccine , as of 2014 , the only widespread and effective solutions to an ebola outbreak remain isolation , sanitation , and information .

and as the virus spreads , it invades the lymph nodes and vital organs , such as kidneys and liver , causing them to lose function . but the virus itself is not what kills ebola victims . instead , the mounting cell deaths trigger an immune system overload , known as a cytokine storm , an explosion of immune responses that damages blood vessels , causing both internal and external bleeding .

where does the ebola virus get its name ?

this is a thought experiment . let 's say at some point in the not so distant future , you 're barreling down the highway in your self-driving car , and you find yourself boxed in on all sides by other cars . suddenly , a large , heavy object falls off the truck in front of you . your car ca n't stop in time to avoid the collision , so it needs to make a decision : go straight and hit the object , swerve left into an suv , or swerve right into a motorcycle . should it prioritize your safety by hitting the motorcycle , minimize danger to others by not swerving , even if it means hitting the large object and sacrificing your life , or take the middle ground by hitting the suv , which has a high passenger safety rating ? so what should the self-driving car do ? if we were driving that boxed in car in manual mode , whichever way we 'd react would be understood as just that , a reaction , not a deliberate decision . it would be an instinctual panicked move with no forethought or malice . but if a programmer were to instruct the car to make the same move , given conditions it may sense in the future , well , that looks more like premeditated homicide . now , to be fair , self-driving cars are are predicted to dramatically reduce traffic accidents and fatalities by removing human error from the driving equation . plus , there may be all sorts of other benefits : eased road congestion , decreased harmful emissions , and minimized unproductive and stressful driving time . but accidents can and will still happen , and when they do , their outcomes may be determined months or years in advance by programmers or policy makers . and they 'll have some difficult decisions to make . it 's tempting to offer up general decision-making principles , like minimize harm , but even that quickly leads to morally murky decisions . for example , let 's say we have the same initial set up , but now there 's a motorcyclist wearing a helmet to your left and another one without a helmet to your right . which one should your robot car crash into ? if you say the biker with the helmet because she 's more likely to survive , then are n't you penalizing the responsible motorist ? if , instead , you save the biker without the helmet because he 's acting irresponsibly , then you 've gone way beyond the initial design principle about minimizing harm , and the robot car is now meting out street justice . the ethical considerations get more complicated here . in both of our scenarios , the underlying design is functioning as a targeting algorithm of sorts . in other words , it 's systematically favoring or discriminating against a certain type of object to crash into . and the owners of the target vehicles will suffer the negative consequences of this algorithm through no fault of their own . our new technologies are opening up many other novel ethical dilemmas . for instance , if you had to choose between a car that would always save as many lives as possible in an accident , or one that would save you at any cost , which would you buy ? what happens if the cars start analyzing and factoring in the passengers of the cars and the particulars of their lives ? could it be the case that a random decision is still better than a predetermined one designed to minimize harm ? and who should be making all of these decisions anyhow ? programmers ? companies ? governments ? reality may not play out exactly like our thought experiments , but that 's not the point . they 're designed to isolate and stress test our intuitions on ethics , just like science experiments do for the physical world . spotting these moral hairpin turns now will help us maneuver the unfamiliar road of technology ethics , and allow us to cruise confidently and conscientiously into our brave new future .

governments ? reality may not play out exactly like our thought experiments , but that 's not the point . they 're designed to isolate and stress test our intuitions on ethics , just like science experiments do for the physical world . spotting these moral hairpin turns now will help us maneuver the unfamiliar road of technology ethics , and allow us to cruise confidently and conscientiously into our brave new future .

how are these thought experiments like science experiments ?

statistics are persuasive . so much so that people , organizations , and whole countries base some of their most important decisions on organized data . but there 's a problem with that . any set of statistics might have something lurking inside it , something that can turn the results completely upside down . for example , imagine you need to choose between two hospitals for an elderly relative 's surgery . out of each hospital 's last 1000 patient 's , 900 survived at hospital a , while only 800 survived at hospital b . so it looks like hospital a is the better choice . but before you make your decision , remember that not all patients arrive at the hospital with the same level of health . and if we divide each hospital 's last 1000 patients into those who arrived in good health and those who arrived in poor health , the picture starts to look very different . hospital a had only 100 patients who arrived in poor health , of which 30 survived . but hospital b had 400 , and they were able to save 210 . so hospital b is the better choice for patients who arrive at hospital in poor health , with a survival rate of 52.5 % . and what if your relative 's health is good when she arrives at the hospital ? strangely enough , hospital b is still the better choice , with a survival rate of over 98 % . so how can hospital a have a better overall survival rate if hospital b has better survival rates for patients in each of the two groups ? what we 've stumbled upon is a case of simpson 's paradox , where the same set of data can appear to show opposite trends depending on how it 's grouped . this often occurs when aggregated data hides a conditional variable , sometimes known as a lurking variable , which is a hidden additional factor that significantly influences results . here , the hidden factor is the relative proportion of patients who arrive in good or poor health . simpson 's paradox is n't just a hypothetical scenario . it pops up from time to time in the real world , sometimes in important contexts . one study in the uk appeared to show that smokers had a higher survival rate than nonsmokers over a twenty-year time period . that is , until dividing the participants by age group showed that the nonsmokers were significantly older on average , and thus , more likely to die during the trial period , precisely because they were living longer in general . here , the age groups are the lurking variable , and are vital to correctly interpret the data . in another example , an analysis of florida 's death penalty cases seemed to reveal no racial disparity in sentencing between black and white defendants convicted of murder . but dividing the cases by the race of the victim told a different story . in either situation , black defendants were more likely to be sentenced to death . the slightly higher overall sentencing rate for white defendants was due to the fact that cases with white victims were more likely to elicit a death sentence than cases where the victim was black , and most murders occurred between people of the same race . so how do we avoid falling for the paradox ? unfortunately , there 's no one-size-fits-all answer . data can be grouped and divided in any number of ways , and overall numbers may sometimes give a more accurate picture than data divided into misleading or arbitrary categories . all we can do is carefully study the actual situations the statistics describe and consider whether lurking variables may be present . otherwise , we leave ourselves vulnerable to those who would use data to manipulate others and promote their own agendas .

and what if your relative 's health is good when she arrives at the hospital ? strangely enough , hospital b is still the better choice , with a survival rate of over 98 % . so how can hospital a have a better overall survival rate if hospital b has better survival rates for patients in each of the two groups ? what we 've stumbled upon is a case of simpson 's paradox , where the same set of data can appear to show opposite trends depending on how it 's grouped .

at first , which hospital appears to have the better survival rate ?

imagine being a fossil : touring the world 's great museums , inspiring awe in onlookers of all ages , posing for hordes of fawning photographers . sound like something you 'd like ? well , good luck ! at least 99.9 % of creatures that have ever lived are n't preserved in the fossil record . but forget about them , everyone else will , and listen up ! if you want your corpse in the exclusive 0.01 % club , the hall of preserved fossil fame , it will not be easy . you better work ! step one : die . it 's a cold , hard fact of fossilization . everything paleontologists find was once alive and , at some point , died . we 'll skip the details and assume you had a long , fulfilling life so we can get to what is really important -- how you die . there are many ways to become a fossil , so let 's highlight your top death options . you could get yourself trapped in tree sap , which , when hardens , turns into amber and can survive intact for millions of years . but unless you find a really big tree to sit under , amber preservation will likely remain the domain of insects and other very small animals . generally , the right place to be if you want to end up a fossil is wherever sediment is actively being deposited , like a lake or an ocean floor . a mountaintop or prairie ? not good ! you need to get buried , the faster the better , because the longer you hang around on the surface , the more likely you 'll get eaten , scavenged , or otherwise destroyed before ever having a chance to get preserved . if you can get buried someplace with little to no oxygen , like a bog or a deep lake bottom , even better . that lack of oxygen will slow down your decay and give you more time to fossilize . so , let 's say you 're lucky enough to die and get buried in a shallow sea under muddy , sandy sediments . what 's your next move ? one option is a process called permineralization . while all your soft parts decay away , your bones get saturated with mineral-rich waters . bit by bit , microscopic crystals precipitate out of these waters to fill in the empty spaces and pores in your bones . otherwise , you 'd better hope the sediments around you harden while your bones decay away and another sediment or mineral fills in the spaces your bones leave behind , creating a perfect cast of your skeleton . over time , the sediments around your fossil will lithify or turn into rock . but you 're not in the clear yet ! many things could happen to those sedimentary rocks that might destroy your chances of getting discovered . they could get uplifted into a mountain range and eroded away or carried along in an oceanic plate and subducted back into the earth 's mantle , melting your fossil into hot mush . fingers crossed your rock surroundings will get gently lifted up by plate tectonics , sea levels will change , and you 'll end up under dry land close to the surface , but not so close that erosion from wind and rain wipes you away before someone can come find you . the last step in this long process , an intrepid paleontologist has to come find you . maybe she 's a research scientist scouting for fossils your age and type or just an amateur collector hoping for a fortuitous find . she whacks away at layers of rock above you or spots your fossil exposed in a creek bank after a flood . and there you are , a magnificent scientific discovery , millions of years in the making ! she and her colleagues gently extract you from the surrounding sediment , measure and photograph all the bits and pieces they find , and begin the complex task of reconstructing how and when you lived based on the evidence they find in your bones . paleontologists will be some of your biggest fans along with all those admiring crowds at the museum . you made it ! you spent years underground in obscurity , shedding blood , sweat , tears , and your internal organs . you worked yourself to the bone until your bones disintegrated and were replaced by minerals and sediments . but it was all worth it because you 're a famous fossil ! now , you better hold that pose !

a mountaintop or prairie ? not good ! you need to get buried , the faster the better , because the longer you hang around on the surface , the more likely you 'll get eaten , scavenged , or otherwise destroyed before ever having a chance to get preserved .

would a dry cave be a good place for permineralization to occur ?

imagine setting sail from hawaii in a canoe . your target is a small island thousands of kilometers away in the middle of the pacific ocean . that 's a body of water that covers more than 160 million square kilometers , greater than all the landmasses on earth combined . for thousands of years , polynesian navigators managed voyages like this without the help of modern navigational aids . ancient polynesians used the sun , moon , stars , planets , ocean currents , and clouds as guides that allowed them to see the ocean as a series of pathways rather than an obstacle . their voyages began around 1500 b.c . when the people who would settle polynesia first set sail from southeast asia . early polynesians eventually settled a vast area of islands spread over 40 million square kilometers of the pacific ocean . some historians believe the voyagers moved from place to place to avoid overpopulation . others , that they were driven by war . voyages became less frequent by around 1300 a.d. as polynesian societies became more rooted in specific locations . during the voyaging period , successful journeys depended on a number of factors : well-built canoes , the skill of navigators , and weather being some of the biggest . voyages relied on sturdy wa'a kaulua , or double-hulled canoes , which were powered by sails and steered with a single large oar . canoe building involved the whole community , bringing together the navigators , canoe builders , priests , chanters , and hula dancers . navigators were keen observers of the natural world . they were abundantly familiar with trade wind-generated ocean swells , which typically flow northeast or southeast . by day , navigators could identify direction by the rocking motion of their canoes caused by these swells . but sunrise and sunset were even more useful . the sun 's position indicated east and west and created low light on the ocean that made it possible to see swells directly . at night , navigators used something called a star compass , which was n't a physical object , but rather a sort of mental map . they memorized the rising and setting points of stars and constellations at different times of the year . they used those to divide the sky into four quadrants , subdivided into 32 houses , with the canoe in the middle . so , for example , when they saw the star pira ‘ atea rising from the ocean , they knew that to be northeast . they had some other tricks , too . the earth 's axis points towards hokupa'a , or the north star , so called because it 's the one fixed point in the sky as the earth rotates and always indicates north . however , it 's not visible south of the equator , so navigators there could use a constellation called newe , or the southern cross , and some mental tricks to estimate where south is . for instance , draw a line through these two stars , extend it 4.5 times , and draw another line from there to the horizon . that 's south . but the sky also contains navigational aids much closer to earth , the clouds . besides being useful weather cues , under the right conditions , they can indicate landmasses . for instance , the lagoons of pacific atolls can actually be seen reflected on the underside of clouds , if you know what to look for . and high masses of clouds can indicate mountainous islands . once navigators neared their destination , other clues , such as the flight patterns of birds , floating debris or vegetation , and types of fish in the area helped determine the proximity of land . for example , the manu-o-ku had a known flight range of 190 kilometers , and could be followed back to shore . so how do we know all of this ? partially through evidence in petroglyphs , written observations of european explorers , and polynesian oral traditions . but also by trying them out for ourselves . in 2017 , a voyaging canoe called hokulea completed a worldwide voyage using only these techniques . if that seems remarkable , remember the ancient polynesians , who through close study and kinship with nature , were able to forge these paths across an unfathomably vast , vibrant living ocean .

that 's a body of water that covers more than 160 million square kilometers , greater than all the landmasses on earth combined . for thousands of years , polynesian navigators managed voyages like this without the help of modern navigational aids . ancient polynesians used the sun , moon , stars , planets , ocean currents , and clouds as guides that allowed them to see the ocean as a series of pathways rather than an obstacle .

which item was not used by ancient polynesian navigators ?

would n't it be great if we could be invisible ? ha , right ? i mean , we could spy on people without being noticed and do whatever we want without being held responsible . now , magicians have figured out how to utilize full-sized mirrors to bend light in order to create disappearing illusions . scientists have created metamaterials to guide rays of light around tiny , two-dimensional objects . cameras can also film what is behind you and project the image so you appear invisible from the front . however , none of these options can make an object as large as a person appear invisible for all angles and distances while its moving . but if you are truly invisible , as in from within , here are a few problems you may not have thought about before . to move around undetected by other people , you would have to be totally naked . even if it 's freezing outside ! you ca n't carry anything , including your wallet and keys , otherwise people would just see your wallet and keys floating around . drivers and people on the street ca n't see you either , therefore they can and will run into you at some point . oh , and you better not wear any perfume or make any noise breathing , otherwise they 'll know you 're there . and , just because you start off invisible , does n't mean you 'll stay that way . what if someone accidentally spills scolding hot coffee on you ? and what if it rains ? but if you think only liquid can make you visible , you 're wrong . dust consists of dead skin cells from humans , soil particles , and fibers from clothes made from cotton and other materials . dust sticks to the moisture on our skin when we sweat and the tiny hairs on our skin when we are dry . so , even if you are invisible , dust would still land on every part of you . we usually do n't notice the dust on our skin because we ca n't see a thin layer of dust on top of our skin color . but , if you 're invisible , people would see a human-shaped blob of dust walking around with extremely dirty soles . gross ! what do you think the world looks like if you are invisible ? well , the answer is nothing . the reason you ca n't see in the dark is because there is no light . to see an apple , light has to hit the apple and return it to your eyes . then , the retinas in your eyes catch the light reflection for your brain to interpret into the image of an apple . if you 're invisible , then , by definition , light would travel through you or around you instead of bouncing off you for people to see . but that means that retinas in your eyes are not catching the light , either . therefore , your brain has nothing to interpret into an image . can you see your reflection without a mirror to stop the light ? no . so , when you ca n't be seen by others , you also can not see . ouch ! now , have you given any thought as of whether the invisibility is permanent ? if it is , how can you receive medical treatment from a doctor if you 're injured ? the doctor would n't know where to apply ointments or bandages because they can not access your injury . for that matter , you ca n't see it either . i mean , what if you have an illness or an infection ? how can the doctor diagnose you without being able to see the color change or inflammation ? and what if everyone is permanently invisible ? well , think about how boring the world would be without seeing people on the streets , on tv , or at home on your computer like right now . it 's lonely being invisible . now , which superpower physics lesson will you explore next ? shifting body size and content , super speed , flight , super strength , immortality , and invisibility .

dust sticks to the moisture on our skin when we sweat and the tiny hairs on our skin when we are dry . so , even if you are invisible , dust would still land on every part of you . we usually do n't notice the dust on our skin because we ca n't see a thin layer of dust on top of our skin color .

if a person is invisible , his/her presence can still be detected by other people ’ s sense of :

some superheros can move faster than the wind . the men in apollo 10 reached a record-breaking speed of around 25,000 miles per hour when the shuttle re-entered the earth 's atmosphere in 1969 . would n't we save a lot of time to be able to move that fast ? but what 's the catch ? air is not empty . elements like oxygen and nitrogen , even countless dust particles , make up the air around us . when we move past these things in the air , we 're rubbing against them and creating a lot of friction , which results in heat . just like rubbing your hands together warms them up or rubbing two sticks together makes fire , the faster objects rub together , the more heat is generated . so , if we 're running at 25,000 miles per hour , the heat from friction would burn our faces off . even if we somehow withstood the heat , the sand and dirt in the air would still scrape us up with millions of tiny cuts all happening at the same time . ever seen the front bumper or grill of a truck ? what do you think all the birds and bugs would do to your open eyes or exposed skin ? okay , so you 'll wear a mask to avoid destroying your face . but what about people in buildings between you and your destination ? it takes us approximately one-fifth of a second to react to what we see . by the time we see what is ahead of us and react to it - time times velocity equals distance equals one-fifth of a second times 25,000 miles per hour equals 1.4 miles - we would have gone past it or through it by over a mile . we 're either going to kill ourselves by crashing into the nearest wall at super speed or , worse , if we 're indestructible , we 've essentially turned our bodies into missiles that destroy everything in our path . so , long distance travel at 25,000 miles per hour would leave us burning up , covered in bugs , and leaves no time to react . what about short bursts to a location we can see with no obstacles in between ? okay , let 's say a bullet is about to hit a beautiful damsel in distress . so , our hero swoops in at super speed , grabs her , and carries her to safety . that sounds very romantic , but , in reality , that girl will probably suffer more damage from the hero than the bullet if he moved her at super speed . newton 's first law of motion deals with inertia , which is the resistance to a change in its state of motion . so , an object will continue moving or staying at the same place unless something changes it . acceleration is the rate the velocity changes over time . when the girl at rest , velocity equals zero miles per hour , begins accelerating to reach the speed within seconds , velocity increases rapidly to 25,000 miles per hour , her brain would crash into the side of her skull . and , when she stops suddenly , velocity decreases rapidly back to zero miles per hour , her brain would crash into the other side of her skull , turning her brain into mush . the brain is too fragile to handle the sudden movement . so is every part of her body , for that matter . remember , it 's not the speed that causes the damage because the astronauts survived apollo 10 , it 's the acceleration or sudden stop that causes our internal organs to crash into the front of our bodies the way we move forward in a bus when the driver slams on the brakes . what the hero did to the girl is mathematically the same as running her over with a space shuttle at maximum speed . she probably died instantly at the point of impact . he 's going to owe this poor girl 's family an apology and a big fat compensation check . oh , and possibly face jail time . doctors have to carry liability insurance just in case they make a mistake and hurt their patients . i wonder how much superhero insurance policy would cost . now , which superpower physics lesson will you explore next ? shifting body size and content , super speed , flight , super strength , immortality , and invisibility .

so , an object will continue moving or staying at the same place unless something changes it . acceleration is the rate the velocity changes over time . when the girl at rest , velocity equals zero miles per hour , begins accelerating to reach the speed within seconds , velocity increases rapidly to 25,000 miles per hour , her brain would crash into the side of her skull .

why is it that astronauts can travel that fast without being injured but the girl mentioned above would die ? what is the difference between velocity and acceleration ?

[ ♪ ] a lone explorer on a mission to reveal the grandeur of saturn , its rings and moons [ ♪ ] after 20 years in space nasa 's cassini spacecraft is running out of fuel . and so , to protect moons of saturn that could have conditions suitable for life , a spectacular end has been planned for this long-lived traveler from earth . cassini 's grand finale 5 - 4 - 3 - 2 - 1 [ rockets roar ] and liftoff of the cassini spacecraft on a billion-mile trek to saturn . we have cleared the tower . [ mission audio ] [ ♪ ] in 2004 , following a 7-year journey through the solar system , cassini arrived at saturn . [ mission audio ] june 30 , 2004 saturn orbit insertion the spacecraft carried a passenger , the european huygens probe -- the first human-made object to land on a world in the distant outer solar system . january 14 , 2005 huygens probe landing on titan for over a decade , cassini has shared the wonders of saturn and its family of icy moons , taking us to astounding worlds where methane rivers run to a methane sea . where jets of ice and gas are blasting material into space from a liquid water ocean that might harbor the ingredients for life . [ mission audio ] and saturn -- a giant world ruled by raging storms and delicate harmonies of gravity . [ ♪ ] now , cassini has one last , daring assignment . april 26 , 2017 the grand finale begins . [ ♪ ] cassini 's grand finale is a brand new adventure . [ ♪ ] twenty-two dives through the space between saturn and its rings . [ ♪ ] as it repeatedly braves this unexplored region , cassini seeks new insights about the origins of the rings , and the nature of the planet 's interior -- closer to saturn than ever before . [ ♪ ] on the final orbit , cassini will plunge into saturn fighting to keep its antenna pointed at earth as it transmits its farewell . [ ♪ ] in the skies of saturn , the journey ends , [ ♪ ] as cassini becomes part of the planet itself . [ ♪ ] september 15 , 2017 end of mission . [ ♪ ] nasa jet propulsion laboratory california institute of technology

we have cleared the tower . [ mission audio ] [ ♪ ] in 2004 , following a 7-year journey through the solar system , cassini arrived at saturn . [ mission audio ] june 30 , 2004 saturn orbit insertion the spacecraft carried a passenger , the european huygens probe -- the first human-made object to land on a world in the distant outer solar system .

in what year did cassini launch ?

during a long day spent roaming the forest in search of edible grains and herbs , the weary divine farmer shennong accidentally poisoned himself 72 times . but before the poisons could end his life , a leaf drifted into his mouth . he chewed on it and it revived him , and that is how we discovered tea . or so an ancient legend goes at least . tea does n't actually cure poisonings , but the story of shennong , the mythical chinese inventor of agriculture , highlights tea 's importance to ancient china . archaeological evidence suggests tea was first cultivated there as early as 6,000 years ago , or 1,500 years before the pharaohs built the great pyramids of giza . that original chinese tea plant is the same type that 's grown around the world today , yet it was originally consumed very differently . it was eaten as a vegetable or cooked with grain porridge . tea only shifted from food to drink 1,500 years ago when people realized that a combination of heat and moisture could create a complex and varied taste out of the leafy green . after hundreds of years of variations to the preparation method , the standard became to heat tea , pack it into portable cakes , grind it into powder , mix with hot water , and create a beverage called muo cha , or matcha . matcha became so popular that a distinct chinese tea culture emerged . tea was the subject of books and poetry , the favorite drink of emperors , and a medium for artists . they would draw extravagant pictures in the foam of the tea , very much like the espresso art you might see in coffee shops today . in the 9th century during the tang dynasty , a japanese monk brought the first tea plant to japan . the japanese eventually developed their own unique rituals around tea , leading to the creation of the japanese tea ceremony . and in the 14th century during the ming dynasty , the chinese emperor shifted the standard from tea pressed into cakes to loose leaf tea . at that point , china still held a virtual monopoly on the world 's tea trees , making tea one of three essential chinese export goods , along with porcelain and silk . this gave china a great deal of power and economic influence as tea drinking spread around the world . that spread began in earnest around the early 1600s when dutch traders brought tea to europe in large quantities . many credit queen catherine of braganza , a portuguese noble woman , for making tea popular with the english aristocracy when she married king charles ii in 1661 . at the time , great britain was in the midst of expanding its colonial influence and becoming the new dominant world power . and as great britain grew , interest in tea spread around the world . by 1700 , tea in europe sold for ten times the price of coffee and the plant was still only grown in china . the tea trade was so lucrative that the world 's fastest sailboat , the clipper ship , was born out of intense competition between western trading companies . all were racing to bring their tea back to europe first to maximize their profits . at first , britain paid for all this chinese tea with silver . when that proved too expensive , they suggested trading tea for another substance , opium . this triggered a public health problem within china as people became addicted to the drug . then in 1839 , a chinese official ordered his men to destroy massive british shipments of opium as a statement against britain 's influence over china . this act triggered the first opium war between the two nations . fighting raged up and down the chinese coast until 1842 when the defeated qing dynasty ceded the port of hong kong to the british and resumed trading on unfavorable terms . the war weakened china 's global standing for over a century . the british east india company also wanted to be able to grow tea themselves and further control the market . so they commissioned botanist robert fortune to steal tea from china in a covert operation . he disguised himself and took a perilous journey through china 's mountainous tea regions , eventually smuggling tea trees and experienced tea workers into darjeeling , india . from there , the plant spread further still , helping drive tea 's rapid growth as an everyday commodity . today , tea is the second most consumed beverage in the world after water , and from sugary turkish rize tea , to salty tibetan butter tea , there are almost as many ways of preparing the beverage as there are cultures on the globe .

the war weakened china 's global standing for over a century . the british east india company also wanted to be able to grow tea themselves and further control the market . so they commissioned botanist robert fortune to steal tea from china in a covert operation . he disguised himself and took a perilous journey through china 's mountainous tea regions , eventually smuggling tea trees and experienced tea workers into darjeeling , india . from there , the plant spread further still , helping drive tea 's rapid growth as an everyday commodity .

the british originally traded what for tea ?

your favorite band is great at playing music , but not so great at being organized . they keep misplacing their instruments on tour , and it 's driving their manager mad . on the day of the big concert , the band wakes up to find themselves tied up in a windowless , soundproof practice room . their manager explains what 's happening . outside , there are ten large boxes . each contains one of your instruments , but do n't be fooled by the pictures - they 've been randomly placed . i 'm going to let you out one at a time . while you 're outside , you can look inside any five boxes before security takes you back to the tour bus . you ca n't touch the instruments or in any way communicate what you find to the others . no marking the boxes , shouting , nothing . if each one of you can find your own instrument , then you can play tonight . otherwise , the label is dropping you . you have three minutes to think about it before we start . the band is in despair . after all , each musician only has a 50 % chance of finding their instrument by picking five random boxes . and the chances that all ten will succeed are even lower - just 1 in 1024 . but suddenly , the drummer comes up with a valid strategy that has a better than 35 % chance of working . can you figure out what it was ? pause the video on the next screen if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 here 's what the drummer said : everyone first open the box with the picture of your instrument . if your instrument is inside , you 're done . otherwise , look at whatever 's in there , and then open the box with that picture on it . keep going that way until you find your instrument . the bandmates are skeptical , but amazingly enough , they all find what they need . and a few hours later , they 're playing to thousands of adoring fans . so why did the drummer 's strategy work ? each musician follows a linked sequence that starts with the box whose outside matches their instrument and ends with the box actually containing it . note that if they kept going , that would lead them back to the start , so this is a loop . for example , if the boxes are arranged like so , the singer would open the first box to find the drums , go to the eighth box to find the bass , and find her microphone in the third box , which would point back to the first . this works much better than random guessing because by starting with the box with the picture of their instrument , each musician restricts their search to the loop that contains their instrument , and there are decent odds , about 35 % , that all of the loops will be of length five or less . how do we calculate those odds ? for the sake of simplicity , we 'll demonstrate with a simplified case , four instruments and no more than two guesses allowed for each musician . let 's start by finding the odds of failure , the chance that someone will need to open three or four boxes before they find their instrument . there are six distinct four-box loops . one fun way to count them is to make a square , put an instrument at each corner , and draw the diagonals . see how many unique loops you can find , and keep in mind that these two are considered the same , they just start at different points . these two , however , are different . we can visualize the eight distinct three-box loops using triangles . you 'll find four possible triangles depending on which instrument you leave out , and two distinct paths on each . so of the 24 possible combinations of boxes , there are 14 that lead to faliure , and ten that result in success . that computational strategy works for any even number of musicians , but if you want a shortcut , it generalizes to a handy equation . plug in ten musicians , and we get odds of about 35 % . what if there were 1,000 musicians ? 1,000,000 ? as n increases , the odds approach about 30 % . not a guarantee , but with a bit of musician 's luck , it 's far from hopeless . hi everybody , if you liked this riddle , try solving these two .

let 's start by finding the odds of failure , the chance that someone will need to open three or four boxes before they find their instrument . there are six distinct four-box loops . one fun way to count them is to make a square , put an instrument at each corner , and draw the diagonals .

suppose there are just 6 musicians . how many distinct 6 box loops are there ?

in 1861 , two scientists got into a very brainy argument . specifically , they had opposing ideas of how speech and memory operated within the human brain . ernest aubertin , with his localistic model , argued that a particular region or the brain was devoted to each separate process . pierre gratiolet , on the other hand , argued for the distributed model , where different regions work together to accomplish all of these various functions . the debate they began reverberated throughout the rest of the century , involving some of the greatest scientific minds of the time . aubertin and his localistic model had some big names on his side . in the 17th century , rené descartes had assigned the quality of free will and the human soul to the pineal gland . and in the late 18th century , a young student named franz joseph gall had observed that the best memorizers in his class had the most prominent eyes and decided that this was due to higher development in the adjacent part of the brain . as a physician , gall went on to establish the study of phrenology , which held that strong mental faculties corresponded to highly developed brain regions , observable as bumps in the skull . the widespread popularity of phrenology throughout the early 19th century tipped the scales towards aubertin 's localism . but the problem was that gall had never bothered to scientifically test whether the individual brain maps he had constructed applied to all people . and in the 1840 's , pierre flourens challenged phrenology by selectively destroying parts of animal brains and observing which functions were lost . flourens found that damaging the cortex interfered with judgement or movement in general , but failed to identify any region associated with one specific function , concluding that the cortex carried out brain functions as an entire unit . flourens had scored a victory for gratiolet , but it was not to last . gall 's former student , jean-baptiste bouillaud , challenged flourens ' conclusion , observing that patients with speech disorders all had damage to the frontal lobe . and after paul broca 's 1861 autopsy of a patient who had lost the power to produce speech , but not the power to understand it , revealed highly localized frontal lobe damage , the distributed model seemed doomed . localism took off . in the 1870 's , karl wernicke associated part of the left temporal lobe with speech comprehension . soon after , eduard hitzig and gustav fritsch stimulated a dog 's cortex and discovered a frontal lobe region responsible for muscular movements . building on their work , david ferrier mapped each piece of cortex associated with moving a part of the body . and in 1909 , korbinian brodmann built his own cortex map with 52 separate areas . it appeared that the victory of aubertin 's localistic model was sealed . but neurologist karl wernicke had come up with an interesting idea . he reasoned that since the regions for speech production and comprehension were not adjacent , then injuring the area connecting them might result in a special type of language loss , now known as receptive aphasia . wernicke 's connectionist model helped explain disorders that did n't result from the dysfunction of just one area . modern neuroscience tools reveal a brain more complex than gratiolet , aubertin , or even wernicke imagined . today , the hippocampus is associated with two distinct brain functions : creating memories and processing location in space . we also now measure two kinds of connectivity : anatomical connectivity between two adjoining regions of cortex working together , and functional connectivity between separated regions working together to accomplish one process . a seemingly basic function like vision is actually composed of many smaller functions , with different parts of the cortex representing shape , color and location in space . when certain areas stop functioning , we may recognize an object , but not see it , or vice versa . there are even different kinds of memory for facts and for routines . and remembering something like your first bicycle involves a network of different regions each representing the concept of vehicles , the bicycle 's shape , the sound of the bell , and the emotions associated with that memory . in the end , both gratiolet and aubertin turned out to be right . and we still use both of their models to understand how cognition happens . for example , we can now measure brain activity on such a fine time scale that we can see the individual localized processes that comprise a single act of remembering . but it is the integration of these different processes and regions that creates the coherent memory we experience . the supposedly competing theories prove to be two aspects of a more comprehensive model , which will in turn be revised and refined as our scientific techologies and methods for understanding the brain improve .

he reasoned that since the regions for speech production and comprehension were not adjacent , then injuring the area connecting them might result in a special type of language loss , now known as receptive aphasia . wernicke 's connectionist model helped explain disorders that did n't result from the dysfunction of just one area . modern neuroscience tools reveal a brain more complex than gratiolet , aubertin , or even wernicke imagined .

a model mapping one brain function to one brain area is referred to as :

i love astronomy . you may have noticed . but there ’ s one really frustrating aspect of it : everything we study is really far away . nearly everything we understand about the universe comes from light emitted or reflected by objects . it ’ d be nice if we could get actual samples from them ; physical specimens we could examine in the lab . welp , sometimes the universe can be accommodating , and allows us to hold it in our hands . cambot , can we get this up on still store ? if you go outside on a clear , dark , moonless night — and you really should — chances are pretty good that within a few minutes you ’ ll see a shooting star . it ’ ll zip across the sky , a fiery dot leaving a long glowing trail behind it . they ’ re one of the most exciting and fun things you ’ ll see when you look up , and they always get a gasp and a squeal of delight from people someone who ’ s stargazing . what you ’ re actually seeing is a tiny bit of interplanetary debris : rock , ice , or metal ramming through the earth ’ s atmosphere , heated to incandescence . most are faint , but some can be astonishingly bright ; i saw one once that left an afterimage on my eye ! obviously , shooting stars aren ’ t really stars . so what do we call them ? sometimes it seems like astronomers use different names for objects to keep things as confusing as possible . but really , we do that to separate out different things . in this case , the actual bit of solid stuff coming from space is called a meteoroid . the phenomenon of the meteoroid getting hot and blazing across the sky is called a meteor . and finally , if it hits the ground , we call it a meteorite . i think the second best way to tick off an astronomer is to mix up meteor and meteorite . sometimes astronomers can be pretty pedantic about such things . oh , the best way to tick off an astronomer ? ask them , “ hey , what ’ s your sign ? ” amazingly , a typical meteor that you ’ ll see is due to a meteoroid that ’ s tiny , probably smaller than a grain of sand ! how can that be ? it ’ s because they ’ re hauling mass . you heard me . the meteoroid is orbiting the sun , probably at speeds of a few dozen kilometers per second . as it approaches the earth , our planet ’ s gravity accelerates it an additional 11 kilometers per second — earth ’ s escape velocity . and when it enters our atmosphere it ’ s moving incredibly fast , up to 70 km/sec or more . the energy of motion is called kinetic energy . if you want to get something moving , you have to give it energy , and if you want it to stop , you have to take that energy away . this kinetic energy depends on the mass of the object and how fast it ’ s moving . in fact , it depends on the square of the velocity ; double its speed and it ’ ll have four times the kinetic energy . meteoroids may usually be small , but they ’ re screaming fast , and have a huge amount of kinetic energy . as they hit our atmosphere they slow from their ridiculous orbital speed to nearly a standstill , and all that energy has to go somewhere . it gets converted into light and heat , and that ’ s what we see as a meteor . a big misconception about meteors is that they get hot due to friction with air . actually , a far bigger contributor to their heat is compression . one of the most basic laws of physics is that when you compress a gas it heats up . and a meteoroid coming in at hypersonic speeds compresses the air in front of it a lot , heating it hugely . the gas can reach temperatures of thousands of degrees celsius for a few seconds . the air radiates away this heat , in turn heating up the meteoroid . the material on the surface vaporizes and blows away—a process called ablation . that ablated material leaves a glowing trail behind the meteor , which we call a train . sometimes it can glow for several minutes , getting twisted up in high altitude winds , leaving behind an eerie , ghost-like persistent train . this all happens high above your head , about 90 – 100 km above the ground . typically , from any one location , you can see a few meteors per hour . it may not seem like much , but when you add them up all over the planet you find the earth is getting pelted to the tune of about 100 tons of material a day . but again , most of these meteoroids are teeny tiny . those random meteors are called sporadic meteors . they tend to be rocky in composition , and generally come from asteroids . if two asteroids smack into each other , the collision can eject little bits of material that then orbit the sun on their own . if their orbit crosses the earth , then you have a potential meteor . it may take a few million years , but at some point the earth and the meteoroid are at the same place at the same time , and boom . but sometimes meteoroids travel in packs . when that happens , we can get meteor showers , many dozens or even hundreds of meteors per hour . with one exception , those don ’ t come from asteroids : they come from comets . when a comet orbits the sun , the ice on it turns to gas , dislodging dust and gravel mixed in . this material leaves the comet and tends to stay more or less in the same orbit as the comet itself . over time , that material gets scattered all along the orbit , creating a puffy ribbon of tiny pieces of space debris around the sun . when the earth plows through that cloud of debris , we get a meteor shower . from our viewpoint on earth we see meteors shooting across the sky , apparently radiating away from a single point . that ’ s a perspective effect ; it ’ s like driving through a tunnel and seeing the tiles on the wall and ceiling flying past you , all apparently coming from a point ahead of you . the point in the sky where the meteors come from is called the radiant , and the shower is named after the constellation the radiant ’ s in . so we have the perseid meteor shower , the leonids , the camelopardalids . or the camelopardalids . and , since the earth hits a specific comet stream around the same time every year , the showers are annual . the perseids are in august , and the leonids in november . watching a meteor shower is easy : just go outside and look up ! generally , they ’ re better after local midnight . the earth plows into the meteoroids , so facing the direction of earth ’ s orbital motion means more meteors , just like you get more raindrops on the front windshield of your car than than on the back when driving through a storm . after local midnight you ’ re on the part of the earth facing into the orbit , so you see more meteors . by the way , if you happen to be on the international space station , you have to look down to see a meteor . in 2011 , astronaut ron garan photographed a perseid burning up below him ! but don ’ t worry : the odds of the space station getting hit are extremely low . space is big . oh , and that one exception i mentioned before ? that ’ s the annual geminids shower , which occurs in december . that comes from the asteroid 3200 phaethon , which is on an orbit that takes it very close to the sun . it ’ s possible it gets so hot that the rock vaporizes , making it act like a comet . the vast majority of meteoroids are small and tend to burn up in our atmosphere . but they can be bigger . a bolide , or fireball , is an extremely bright meteor , and those can be about the size of a grapefruit . those happen pretty often somewhere over the earth . i ’ ve seen a few myself . very rarely , an incoming meteoroid will survive all the way to the ground and become a meteorite . sometimes , the immense pressure of ramming earth ’ s air causes the incoming meteoroid to crumble or even explode , raining down dozens or hundreds of smaller pieces . typically , they slow rapidly after their blaze of glory , and simply fall the rest of the way to the ground . the air up there is cold , and their interiors are cold from being in space so long . so , despite what you might think , meteorites don ’ t cause fires when they hit the ground . in fact , they can be quite chilly ! meteorites are classified into three broad categories : stony , which are mostly rock ; iron , which are mostly metal ; and stony iron , which are a mixture of the two . the majority of meteorites we find are stony . the stony meteorites are subdivided into two kinds : chondrites , and achondrites . chondrites contain chondrules , small grains of minerals . these are very primitive , and are thought to have condensed out of the original disk of material that formed the solar system . their age can be found by looking at ratios of elements in them formed from radioactive decay . the oldest known meteorite formed 4.568 billion years ago : before the earth itself formed ! achondrites don ’ t have chondrules in them . most likely they came from a bigger asteroid , one that was once molten through , mixing the minerals . a big collision disrupted the parent body , creating the achondritic meteoroids . iron meteorites most likely come from the center of a large asteroid , one big enough that metals fell to the center via gravity . again , a big impact blew the asteroid up , scattering its material around the asteroid belt , and with some on orbits that eventually intersected earth . stony irons are the rarest . some have green or orange crystals of a mineral called olivine embedded in a web of metal . called pallasites , they may be the most beautiful of all meteorites . i actually collect meteorites . it ’ s fun but can be a somewhat pricey hobby . if you ’ re interested , make sure you get ‘ em from a licensed dealer . we have links to some in the dooblydoo . of course , on occasion the meteoroid coming in can be a tad bigger . and when that happens , well , all hell can break loose . on february 15 , 2013 , residents of the russian city of chelyabinsk got a rude awakening . at 9:20 a.m. local time , a rock about 19 meters across came in at a low angle . it got nearly as bright as the sun as it slammed into the atmosphere , and the pressure of its passage broke it up into several chunks , which broke up again . in a moment ’ s time , the sudden energy released was equivalent to the detonation of a half million tons of tnt — as much as a small atomic bomb ! while no one was killed , over a thousand people were injured by flying glass , shattered by the explosion . no doubt they were at their windows gawking at the huge vapor trail in the sky when the shock wave hit . there was no warning for this event ; the asteroid was essentially too small to detect while it was out in space . well , for now at least . telescopes are coming online soon that should be able to find smaller asteroids and give us some warning . astronomers are more worried about ones roughly a hundred meters across or bigger ; these can do serious damage on a city-wide scale or larger , but at the moment aren ’ t easy to spot much in advance . and what do we do if we do see one headed our way ? as of right now , there ’ s not much we can do . studies have been done to determine the best course of action ; maybe lobbing a nuke at it , or simply ramming it with a spaceprobe to change the orbit and make sure it misses earth . these ideas look good on paper , but they haven ’ t been tested yet . we ’ re still a few years from that . the good news is that objects that size hitting the earth are rare ; maybe once every century or three . but if we do nothing , it will happen eventually . as science fiction writer larry niven points out , the dinosaurs went extinct because they didn ’ t have a space program . hopefully , we ’ re smarter than they were . today you learned that meteors are small bits of interplanetary debris sloughed off by asteroids and comets . when the earth plows through the stream emitted by a comet we get a meteor shower . meteors burn up about 100 km above the earth , but some survive to hit the ground . most of these meteorites are rocky , some are metallic , and a few are a mix of the two . very big meteorites can be a very big problem , but there are plans in the works to prevent us from going the way of the dinosaurs . crash course astronomy - hey crash course , meteors ! cool ! crash course astronomy is produced in association with pbs digital studios . head over to their channel for even more awesome videos . this episode was written by me , phil plait . the script was edited by blake de pastino , and our consultant is dr. michelle thaller . it was directed by nicholas jenkins , the script supervisor and editor is nicole sweeney , the sound designer was michael aranda , and the graphics team is thought café .

with one exception , those don ’ t come from asteroids : they come from comets . when a comet orbits the sun , the ice on it turns to gas , dislodging dust and gravel mixed in . this material leaves the comet and tends to stay more or less in the same orbit as the comet itself .

when comets orbit the sun , the ice on them turns to gas , dislodging dust and gravel that fall away from the comet but stay in orbit , creating a puffy ribbon of debris orbiting the sun . what is the phenomenon called when earth 's orbit crosses this ribbon ?

if you 've got a cold , mucus is hard to miss . but what is it , and what does it do besides making you miserable ? your body produces more than a liter of mucus every day , and all the wet surfaces of your body that are not covered by skin , like your eyes , nose , mouth , lungs , and stomach get a liberal coating . that 's why they 're known as mucus membranes . mucus plays lots of roles in your body . it keeps delicate tissues from drying out and cracking , which would expose them to infection . it lubricates your eyes so you can blink . it protects your stomach lining from acid . it neutralizes threats by removing or trapping substances that could make you sick . and finally , it houses and keeps your body 's trillions of bacterial inhabitants , your microbiota , under control . mucus contains lots of different compounds , including proteins , fats , and salts . but a key component of mucus versatility is a set of proteins called mucins . mucins are the primary large molecules in mucus and are essential for giving mucus its slippery feel . they belong to a class of proteins called glycoproteins which are built out of both amino acids and sugars . in mucin , long chains of sugars are attached to specific amino acids in the protein backbone . the hydrophilic sugar chains help mucin dissolve in your body 's watery fluids . mucus , which is up to 90 % water , stays hydrated thanks to these sugar chains . some of these mucins can interact with other mucin molecules to create a complex network that establishes a barrier against pathogens and other invaders . that 's why mucus is the body 's first line of defense against foreign objects , like bacteria and dust . it 's continuously produced to clear them from the respiratory tract , like a slimy conveyor belt . this keeps bacteria from getting a solid purchase on delicate lung tissue , or making it to the blood stream , where they could cause a major infection . many of those harmful bacteria also cause diseases when they cluster into slimy growths called biofilms . but mucus contains mucins , antimicrobial peptides , antibodies , and even bacteria-hungry viruses called bacteriophages that all work together to prevent biofilms from forming . if microbes do become harmful and you get sick , the body ramps up mucus production to try to quickly flush out the offenders , and the immune system floods your mucus with extra white blood cells . in fact , the greenish mucus often associated with infections gets its color from an enzyme produced by those white blood cells . this multi-pronged approach to bacterial management is one of the main reasons why we 're not sick all the time . even though mucus protects against the infectious bacteria , the vast majority of your body 's bacterial tenants are not harmful , and many are actually beneficial . that 's particularly true when they live in mucus , where they can perform important functions , like synthesizing vitamins , suppressing harmful inflammation , and controlling the growth of more harmful species . so even though you probably associate mucus with being ill , it 's really helping you stay healthy . sure , it might seem gross , but can you think of any other substance that can lubricate , keep your body clean , fight infection , and domesticate a teeming bacterial population ? nope , just mucus .

sure , it might seem gross , but can you think of any other substance that can lubricate , keep your body clean , fight infection , and domesticate a teeming bacterial population ? nope , just mucus .

which other living organisms produce significant amounts of mucus as an integral part of their physiology ?

interviewer : danica , how are you ? good , good . interviewer : nice to see you , what are you studying right now ? i 'm studying geometry . interviewer : holy cow , look at that . when i was in the ninth grade , i remember studying geometry theorems and saying , `` would n't it be cool to have a theorem named after me ? '' and i had no idea that one day , that would happen . intro winnie cooper ( character ) : hey kevin , hi paul ! paul ( character ) : winnie cooper ? ! winnie cooper was the girl next door . winnie cooper ( character ) : my real name is gwendolyn . she was the love interest , on again and off again of kevin arnold kevin arnold ( character ) : winnie will you go to the dance with me ? winnie cooper ( character ) : dance ? ... i ca n't her parents had a lot of issues . they 're separated and winnie had to move . it was a sort of deep sadness to winnie cooper . and it kind of helped kevin to appreciate his own family sometimes . winnie cooper was very smart . she scored better than -- kevin arnold on the sats . kevin arnold ( character ) : what exactly did you do get on your sats ? winnie cooper ( character ) : 725 verbal , 757 math . yeah . she was smart . clip : `` you fell in love with them five years ago . and you watched them grow up . -- the wonder years , a special one hour final episode . '' any child whose been on a very popular series knows that when it 's over , there 's a difficult period , where there 's a lot of insecurity . you 're so recognized for this one role . and then when that 's over , you start to wonder well , who else would i be if i did n't have this role ? so , i then went to ucla and in my mind i thought , okay , new chapter of my life , i 'm moving on . and of course , i got to the ucla campus and everybody was like `` hey winnie , where 's kevin ? '' it happened over and over and over again and i really just wanted to move on and figure out who i was . i was like , god you guys , this is hard enough , stop . i was going to be a film major . but i decided to take this math class . i was like , `` i do n't know if i can do this . '' i was afraid of it . i was afraid of it . i 'd gotten a five on the ap calculus bc exam , which is the highest score you can get on the most difficult calculus exam offered in high school . and i did n't think i 'd do well ? who did i think would do well ? somebody who looked the part more than me . when i took my first multivariable calculus class , i scored at the top of the class . a hundred and sixty three people . the professor actually graphed the scores on the chalkboard . i 'll never forget it . my score was the twenty two and then two fifteens and then it was nine and below . and i was stunned , i was floored , i could not believe that i 'd done so well . the professor came up to me and said , `` you have a gift in math . -- you should really pursue this . you should be a math major . '' ... .what ? a math major ? '' i thought that a math class in college would be hard enough . a couple days later , in that class , this kid tapped me on the shoulder and said `` excuse me are you that girl ? '' and that question always ends with , `` from tv ? '' or `` who played winnie ? '' he goes , `` excuse me , are n't you that girl who got the 22 ? i was like ... `` yes ... that is me . '' i became a calculus tutor in the department , i excelled in my classes and i loved it . i had the opportunity to co-author a research paper . we proved a new theorem . percolation and gibbs states multiplicity for ferromagnetic ashkin-teller models on z two . also known now as the chayes-mckellar-winn theorem . i discovered that i could be smart and capable and valuable for something that had nothing to do with hollywood . this is me . and it felt great .

intro winnie cooper ( character ) : hey kevin , hi paul ! paul ( character ) : winnie cooper ? ! winnie cooper was the girl next door . winnie cooper ( character ) : my real name is gwendolyn .

danica was used to hearing the question : `` are n't you the girl from 'the wonder years ' ? '' what question did she finally hear in college that helped her realize she was more than just winnie cooper ?

as your country 's top spy , you must infiltrate the headquarters of the evil syndicate , find the secret control panel , and deactivate their death ray . but all you have to go on is the following information picked up by your surveillance team . the headquarters is a massive pyramid with a single room at the top level , two rooms on the next , and so on . the control panel is hidden behind a painting on the highest floor that can satisfy the following conditions : each room has exactly three doors to other rooms on that floor , except the control panel room , which connects to only one , there are no hallways , and you can ignore stairs . unfortunately , you do n't have a floor plan , and you 'll only have enough time to search a single floor before the alarm system reactivates . can you figure out which floor the control room is on ? pause now to solve the riddle yourself . answer in : 3 answer in : 2 answer in : 1 to solve this problem , we need to visualize it . for starters , we know that on the correct floor there 's one room , let 's call it room a , with one door to the control panel room , plus one door to room b , and one to c. so there must be at least four rooms , which we can represent as circles , drawing lines between them for the doorways . but once we connect rooms b and c , there are no other connections possible , so the fourth floor down from the top is out . we know the control panel has to be as high up as possible , so let 's make our way down the pyramid . the fifth highest floor does n't work either . we can figure that out by drawing it , but to be sure we have n't missed any possibilities , here 's another way . every door corresponds to a line in our graph that makes two rooms into neighbors . so in the end , there have to be an even number of neighbors no matter how many connections we make . on the fifth highest floor , to fulfill our starting conditions , we 'd need four rooms with three neighbors each , plus the control panel room with one neighbor , which makes 13 total neighbors . since that 's an odd number , it 's not possible , and , in fact , this also rules out every floor that has an odd number of rooms . so let 's go one more floor down . when we draw out the rooms , low and behold , we can find an arrangement that works like this . incidentally , the study of such visual models that show the connections and relationships between different objects is known as graph theory . in a basic graph , the circles representing the objects are known as nodes , while the connecting lines are called edges . researchers studying such graphs ask questions like , `` how far is this node from that one ? '' `` how many edges does the most popular node have ? '' `` is there a route between these two nodes , and if so , how long is it ? '' graphs like this are often used to map communication networks , but they can represent almost any kind of network , from transport connections within a city and social relationships among people , to chemical interactions between proteins or the spread of an epidemic through different locations . so , armed with these techniques , back to the pyramid . you avoid the guards and security cameras , infiltrate the sixth floor from the top , find the hidden panel , pull some conspicuous levers , and send the death ray crashing into the ocean . now , time to solve the mystery of why your surveillance team always gives you cryptic information . hi everybody . if you liked this riddle , try solving these two .

so in the end , there have to be an even number of neighbors no matter how many connections we make . on the fifth highest floor , to fulfill our starting conditions , we 'd need four rooms with three neighbors each , plus the control panel room with one neighbor , which makes 13 total neighbors . since that 's an odd number , it 's not possible , and , in fact , this also rules out every floor that has an odd number of rooms . so let 's go one more floor down .

if the problem were changed such that all rooms were connected to three other rooms and one room was connected to four other rooms , then what would the minimum number of rooms have been ?

translator : tom carter reviewer : bedirhan cinar dialogue gives a story color , makes it exciting and moves it forward . romeo : o , wilt thou leave me so unsatisfied ? juliet : what satisfaction canst thou have tonight ? romeo : the exchange of thy love 's faithful vows for mine . without dialogue : ( cricket sounds ) so what goes into writing effective dialogue ? well , there are social skills : making friends , solving conflicts , being pleasant and polite . we wo n't be using any of those today . instead , we 'll be working on -- let 's call them `` anti-social skills . '' if you 're a writer , you may already have a few of these . the first is eavesdropping . if you 're riding a bus and hear an interesting conversation , you could write it all down . of course , when you write fiction , you 're not describing real people , you 're making up characters . but sometimes the words you overhear can give you ideas . `` i did not , '' says one person . `` i saw you , '' the other replies . who might be saying those words ? maybe it 's two kids in a class , and the boy thinks the girl pushed him . maybe it 's a couple , but one of them is a vampire , and the woman vampire saw the man flirting with a zombie . or maybe not . maybe the characters are a teenager and his mother , and they 're supposed to be vegetarians , but the mother saw him eating a burger . so let 's say you 've decided on some characters . this is anti-social skill number two : start pretending they 're real . what are they like ? where are they from ? what music do they listen to ? spend some time with them . if you 're on a bus , think about what they might be doing if they were there too . would they talk on the phone , listen to music , draw pictures , sleep ? what we say depends on who we are . an older person might speak differently than a younger person . someone from the south might speak differently than someone from the north . once you know your characters , you can figure out how they talk . at this stage , it 's helpful to use anti-social skill number three : muttering to yourself . when you speak your character 's words , you can hear whether they sound natural , and fix them if necessary . remember , most people are usually pretty informal when they speak . they use simple language and contractions . so , `` do not attempt to lie to me '' sounds more natural as `` do n't try to lie to me . '' also keep it short . people tend to speak in short bursts , not lengthy speeches . and let the dialogue do the work . ask yourself : do i really need that adverb ? for instance , `` 'your money or your life , ' she said threateningly . '' here , `` threateningly '' is redundant , so you can get rid of it . but if the words and the actions do n't match , an adverb can be helpful . `` 'your money or your life , ' she said lovingly . '' so , to recap : first , eavesdrop . next , pretend imaginary people are real . finally , mutter to yourself , and write it all down . you already have everything you need . this is fictional dialogue , or `` how to hear voices in your head . ''

romeo : the exchange of thy love 's faithful vows for mine . without dialogue : ( cricket sounds ) so what goes into writing effective dialogue ? well , there are social skills : making friends , solving conflicts , being pleasant and polite .

which one of the following skills goes into writing dialogue ?

if you look at cars from the 1970s and cars from the 1990s , there ’ s really one big difference in their designs . the ones from the 70s are boxy , and the ones from the 90s are curvy . for some car models , you can even tell the exact year when that change happened . just look at this commercial for the buick lesabre , showing the 1991 model — and then the 1992 model . see the curves ? let ’ s watch that again . ‘ 91 is boxy , sharp edges . ‘ 92 ? smooth and round . since then , cars have become curvier and curvier . so how did this happen ? when manufacturers started making curvy cars in the 90s , it wasn ’ t a totally new concept . back in the 1930s , streamliners like this chrysler airflow used this sleek design to reduce wind resistance . but as the 50s and 60s rolled around , american streamliners stopped selling well — they were outsold by bigger , boxier cars . gas prices were on fairly steady decline at this point , so streamlining for fuel efficiency was less of a concern . well into the 1970s , just about every car made in america had sharp edges and very few curves . they were basically designed as a series of three boxes — the hood , the cabin , and the trunk . that model worked really well in the us market . but in europe , fuel was always more expensive . in the 60s , a gallon of gas in france cost a whopping 73.1 cents while it was just 31 cents in the us . so european designers started experimenting with more aerodynamic designs to help cars move more easily so they ’ d waste less gas . automakers like porsche , bmw , audi , mercedes-benz — they all started rolling out car models that had curved exteriors . eventually american automakers started to copy the european aerodynamic look to try to attract upscale consumers . the mass market was a different picture . in europe , a designer named uwe bahnsen was the first person to push for a curved design for the average driver , and he did that with the 1982 ford sierra . it was curvier than any car in its class at the time . but critics just laughed at it . and it did n't sell very well at first . it was nicknamed the “ jelly mould ” because of how much it looked like the kind of circular shape you ’ d make jell-o with . but one of the designers from that european ford design team — this guy , jack telnack — took over the us design team in 1980 . american gas prices at this point were skyrocketing due to conflict in the middle east . so telnack brought wind tunnel testing into the design process . he first did that with the 1983 ford thunderbird . but the real breakthrough came a few years later : `` the result was the groundbreaking 1986 ford taurus . '' it might not look that groundbreaking now , but this style was revolutionary at the time . it was a mass market car with curvy edges — and people liked it . “ taurus ! now a north american car with a shape and a feel we ’ ve never seen before… taurus for us ! ” they used it in robocop as the car of the future . the sales basically saved ford , which had really been struggling at the time , and it inspired a whole wave of copycat curvy cars . and streamlining became even more popular because manufacturers were facing new fuel economy regulations in the us . starting in 1978 , the average fuel efficiency of each manufacturer ’ s passenger cars had to meet higher and higher levels . according to one ford designer , aerodynamic design was a much more affordable way to boost efficiency than doing engineering work under the hood . the rise of computer modelling in the 80s also made it easier for car makers to design and manufacture curved lines . all these years later , the influence on today ’ s cars is pretty clear . even the models that we criticize for being ridiculously boxy these days — like the scion xb — are actually really round . and if our modern day sci fi movies have anything to say about it , that won ’ t be changing anytime soon .

it might not look that groundbreaking now , but this style was revolutionary at the time . it was a mass market car with curvy edges — and people liked it . “ taurus !

during this boxy car period , certain curvy cars were manufactured in america , but they were marketed towards upscale clients . why ?

global oneness project a game for life i do n't know how i can really put this , but my football is really something that is very powerful in my life , that gives me the drive to be who i am now , and have the goals i have now . i think if it was n't for football… i ca n't really imagine myself without football . certain things , certain principles in my life are based on my football . i do n't know if you understand what i mean . [ ♪ native music ♪ ] [ children playing ] [ ♪ native music ♪ ] this is my place . its a very small place . its just a four room house . this is where we sit as a family , watch tv , eat supper , and chat . just family chats . i 'll show you the kitchen where we cook our dinner . this is my kitchen . its not a very big place but it is where i live . this is my bedroom ; i share it with my aunt , but unfortunately now she is asleep because she was working night shift . this is my bed . i sleep here with my kitten . oh yes , this is my kitten . it is my friend . i sleep with her almost every night . this is my aunt . she stays here . she is selling veggies and fruit and her business is definitely going very well . in one week you find that you come and buy something and then its not there , its finished . so she 's got a business that is doing well . this road that we are walking on , this is where i started playing soccer when i got to port elizabeth . we put small stones , there would be goals on each side of the road , then we 'd be playing with the guys . that was before there was grass here . there was no grass here , so we would play from that wall to this side of the road . i grew up playing here and when i see this road or when i walk here i always remember where i started playing soccer . [ ♪ native music ♪ ] most of the time i was with my other two cousin-brothers , and they would spend most of their time playing soccer and that 's how i got on to the field and played as well . [ ♪ native music ♪ ] when i was growing up i was very , very poor . when i was still in primary school , i would wash with cold water . my school shoes , the sole was broken , so when it was raining , my socks would be so wet . and in terms of food , there was absolutely nothing to eat . [ ♪ native music ♪ ] for me to be able to eat at school i would have to wait until we are writing a test . then each pupil would put on 10 cents or 20 cents . then the whole amount would go to the person who was the highest on a test , and that is how i would manage to eat , because , if we were writing a test and put on some money , it was definitely my money because i was a very good student . [ ♪ native music ♪ ] i know their are many people out there who are going through what i went through . i know they wo n't deal with it the way i dealt with it , because i was taking everyday as it was coming . [ ♪ native music ♪ ] i never thought of going out and being a prostitute or something , and i know other people who are going through that thing . always , not always , but sometimes opt for that if they are girls , and if they are boys , they go to armed robbery , bad things like that . so the main reason i always tell the story is just to let them know that poverty can not conquer you for the rest of your life . you can conquer poverty as well . [ ♪ native music ♪ ] [ dog barking ] [ ♪ native music ♪ ] there is a way that you can go . there is a solution to poverty . they always do things that are unethical because they say they are going through poverty . [ ♪ native music ♪ ] i 've never done anything to anyone when i was very poor , but here i am today . i 'm not as poor as i was before and for me , now , i do n't feel like i 'm poor , even though i do n't have everything i want . i do n't have a big house , i do n't have a car , but i still feel that i am rich because i am rich inside . [ speaking in native language ] [ laughter ] this is a very good friend of mine . i grew up playing with him on the street . he was never a very good player , but a very good goal keeper . [ laughter ] come try it : [ gaming device sounds ] [ winning tune ] [ quarters hitting the metal return ] i 've won . it 's my lucky day . there you go , that 's all the money . [ ♪ native hip-hop music ♪ ] soccer helped me to stay away from the option of being a prostitute . i have always had love for my football and discipline . if you are going to be doing all the wrong things to try and get something to eat , or money , then those things wo n't be in-line with your football . if you look at soccer , the things you do that are in line with football , they are also in line with your own life . [ ♪ native hip-hop music ♪ ] people love soccer , and the young kids out there , they are interested in soccer . if you talk about soccer , they all know what you 're talking about , because everyone knows about soccer . so its easy to reach out to the people with soccer . [ ♪ native hip-hop music ♪ ] grassroots soccer we have the kids who know how to prevent themselves from getting hiv and also to teach them life skills . [ ♪ native hip-hop music ♪ ] the older guys have gone through things in their lives , but would like to teach the kids so that they could not go through those things . the way we would do is with interactive games . so we do n't really say , `` yeah , we 're going to talk about hiv now . '' some people might just lose interest in it , but simply because its interactive , we do the actual activities where they just learn from them . and its not as if we are telling them what to do , like to abstain . [ ♪ native hip-hop music ♪ ] so why was it not easy to find the ball ? because you could n't see the ball . so remember when we play that game , what did you say ? teacher > yes my girl , say it . student > someone who has the ball is going to be hiv positive . so what does that tell you about hiv ? you ca n't see someone who has hiv . [ clapping ] since we work with kids we use the power of soccer , and we use soccer balls because kids love to play . if you just make them play , especially with our street leagues , the way we do the teaching for hiv and aids gives them time to play soccer . [ ♪ native hip-hop music ♪ ] those are tools for them to be better people , to stay away from things that could destroy their lives . [ ♪ native hip-hop music ♪ ] after we 've done the program , we also assess the change in their attitudes . [ ♪ native hip-hop music ♪ ] [ clapping ] if there 's a big difference where their attitudes were before they went through the program , i would be very happy about that . [ ♪ native music ♪ ] when you 've got something in your heart and you also want someone else to have that same feeling , i do n't know how to say it ... but it 's always important to just share things with other people . it 's just important . if you know you can do something to help the next person , just do it with all your heart . and not expect to get a reward . it really makes more sense to be able to have others help because , really , we can not live in isolation . honestly , we could be a unity here , but what about the others that are not a unity ? we are going to say , yes we are a unity , that is fine for us . they are not a unity , that 's their own problem . it should n't be like that . [ ♪ native music ♪ ] if people could unite . i 'm telling you , i do n't see anything stopping the world from being a better place . i do n't see anything stopping it . [ ♪ native music ♪ ] it does n't take much for soccer to get people together . if there 's a soccer match somewhere , as long as they know that match is somewhere , they will definitely go . it 's really easy for it to unite people . [ ♪ native music ♪ ] for me its really about passion because i love soccer . i love soccer . it just really ... even if i can be stressed out about something , at my training session or at my game , i forget about it . i do n't know what to say about soccer , but that 's the thing about it . i just do n't know what it is . [ ♪ native music ♪ ] nolusindiso `` titie '' plaatjie is 22 years old and lives in port elizabeth south africa . she studied human movement science at nelson mandela metropolitan university and dreams of becoming an engineer . titie is a well-known soccer star , and in 2001 , she was named captain of the provincial team . she has been playing soccer since the age of five . currently working for grassroots soccer as the port elizabeth project coordinator , titie is a key facilitator in raising hiv ? aids awareness among youth and people of her community . she believes that this is a fight for the world . www.globalonenessproject.org

i think if it was n't for football… i ca n't really imagine myself without football . certain things , certain principles in my life are based on my football . i do n't know if you understand what i mean .

“ there are certain principles in my life that are based on my fútbol , ” says titie , the young woman featured in the film . what principles do you think she is referring to ?

how fast are you moving right now ? that seems like an easy question . the first tempting answer is , `` i 'm not moving . '' upon further reflection , you realize that maybe the earth 's motion counts . so , a second tempting answer is , `` 19 miles/second around the sun . '' but then you recall learning that the sun moves around the center of the milky way galaxy , and the milky way moves within the local group of galaxies , and the local group moves within the virgo cluster , and the virgo cluster moves within ... `` how fast are you moving ? '' is not an easy question . when mission control tells astronauts how fast they 're going , there 's always an assumed standard of rest . at the start of the voyage , speeds are given relative to the launchpad . but later , when the launchpad is just one more arbritrary place down there on earth 's spinning surface , speeds are given relative to the idealized , non-spinning pinpoint center of earth . on their way to the moon , apollo astronauts had a hard time answering the question , `` how fast are you moving ? '' speed away from earth was one thing , and speed toward the moon was quite another . that 's because the earth and the moon move relative to one another . ah , of course ! speed is a relative quantity . when captain kirk ask lieutenant sulu if the starship enterprise has reached a speed of warp 7 , sulu should reply , `` relative to what , captain ? '' such a sassy reply may get subordinate starfleet officers in trouble , but it is the only good answer to the question , `` how fast are you moving ? '' this is basic relatively talking . not fancy einsteinian relativity , but good old fashioned ( and still correct ) galilean relativity . galileo seems to have been the first person to realize that there is no such thing as an absolute speed . speeds are relative . this means that speeds only have meaning when they are referred to a reference frame . presumably that reference frame is itself at rest . but then we have to ask again , `` at rest relative to what ? '' because even the concept of rest has lost any hint of absolute meaning . speed is relative , and rest is relative . earth 's speed is 19 miles/second relative to the sun . the enterprise 's speed is warp 7 relative to the center of the milky way galaxy . your speed is zero relative to your easy chair . but depending on where you sit , it is hundreds of miles/hour relative to earth 's center . when we furrow a brow and ask , `` but how fast is earth really moving ? '' we imagine spaceship earth plowing through the ocean of space as it orbits the sun . but space is not an ocean . it has no substance as water does . space is not a thing ; space is nothing . space is no thing . you can move between two points in space , say between earth and mars , but you ca n't move through space . there 's nothing to move through . it 's like trying to say how much a hole weighs . a hole weighs exactly nothing because a hole is nothing . it 's a void , and so is space . to move relative to nothing is meaningless . the concepts of speed and of rest have only relative meaning . they are absolutely meaningless . they mean something only with respect to arbitrarily chosen , artificial frames of reference . if , someday , you are buckled into your spaceship , and you see from the side window , say , a space station whizz by at constant speed , there is no way to know which of you is really moving . neither of you is really moving because there is no deep reality about constant speed . constant speed in a straight line has only relative meaning , a kind of relative reality . does this mean that all motion is relative ? no ! some motions have only relative meaning , but some motions have absolute meaning , are absolutely real . for example , constant speed is relative , but change in speed is absolute . calling something absolute in science means that arbitrary standards are not used in its measurement . it is unambiguously measurable . when your spaceship fires its engines , your change in speed is beyond doubt . you feel it in your stomach , and your ship 's sensors can measure it . outside your window , the passing space station may seem to be changing speed , but the beings inside the station will not feel it . and no sensors can measure it . you are really changing speed , and they are really are not . there 's something absolutely real about changes in speed . the same goes for rotation . if your spaceship is spinning , you can feel it , and your ship 's sensors can measure it . the space station outside may seem to be going around you , but it is you who feels queasy , not the folks in the space station . you are really spinning , and they really are not . there 's something absolutely real about rotation . so , some motions are relative , and some are not . there is no deep reality about constant speed , but changes in speed are deeply real , and so are rotations . we have to be thoughtful in our analysis of everyday experience in order to identify what is deeply real . since we can be fooled by perceptions as basic as speed , maybe every perception deserves careful scrutiny . this is what inspired einstein to his incredible insights about the speed of light and forward time travel . knowing how to identify what is deeply real is tough and important work . if a police officer ever pulls you over for speeding and asks , & amp ; amp ; quot ; do you know how fast you were going ? & amp ; amp ; quot ; an insightful , though perhaps unwise , reply would be , `` relative to what ? '' and then , as you sit in the backseat of the police car and feel it accelerate toward jail , you can add , & amp ; amp ; quot ; but some things are absolute ! & amp ; amp ; quot ;

because even the concept of rest has lost any hint of absolute meaning . speed is relative , and rest is relative . earth 's speed is 19 miles/second relative to the sun .

cite some examples of terrestrial objects relative to which you are currently moving . can you estimate your speed relative to these objects ?

say you 're helping plan a friend 's party , and he sends you a text asking you to `` bring bob , a dj and a clown . '' you 're pretty impressed . you had no idea bob was so multitalented . but when the day arrives , it turns out that he 's not , and you were supposed to bring three different people . as you and bob sit at the silent , clownless party , it occurs to you that the confusion could 've been avoided simply by using another comma after dj . this final comma in a list , placed directly before the main conjunction , such as and , or , or nor , is called the serial comma , or oxford comma . and it has long driven grammar nerds crazy because even major language institutions ca n't agree on whether it should be used . ironically , the oxford comma is more common in the united states , where it 's recommended by the mla , the chicago style manual , and the us government printing office , though not by the ap style book . in the uk and other english-speaking countries , most style guides do not support the comma 's use , with the exception of its namesake , the oxford university press . why not use the serial comma ? one of the main arguments is that the conjunction is usually enough to denote a separate entity . and where it 's not , like in your ill-fated invite list , changing the order of terms will usually do the job . journalists also dislike the comma because it takes up precious space and can make text look cluttered . sometimes , it can even create confusion of its own . for example , if your friend had asked for `` bob , a dj and a puppy , '' you 'd probably figure out that they 're three separate beings . puppies are cute , but they do n't make great djs . with the comma , you may think bob is the dj , and all you need is him and the puppy . the argument over the oxford comma has raised such strong passions over the years that a sort of truce has been reached . the common wisdom is that its use is optional , and depends on whether it will help to avoid confusion . for one thing , you 're supposed to keep your use or avoidance of the oxford comma consistent throughout a whole piece of writing . so , using it only where necessary is not an option . and the very idea of a grammatical rule being optional is a bit odd . imagine that you had n't messed up the party planning , and read the next day that `` everyone had a great time - ninjas , pirates , vikings , old and young . '' if the oxford comma were standard , you would notice it missing and conclude that old and young must describe the awesome guests already listed . but as things stand , you will always wonder whether it means that a bunch of regular , boring kids and old people showed up as well . ultimately , the serial comma may be useful or annoying , but your opinion on it , as for many optional things , probably has something to do with whichever style you were raised on . your high school teachers favored it ? it 's likely you 're still using it . your first editor hated it ? you probably do , too . and maybe so much hairsplitting over a tiny squiggle on a page is a bit silly . after all , there are so many bigger problems to worry about . but sometimes , little things can make a big difference .

as you and bob sit at the silent , clownless party , it occurs to you that the confusion could 've been avoided simply by using another comma after dj . this final comma in a list , placed directly before the main conjunction , such as and , or , or nor , is called the serial comma , or oxford comma . and it has long driven grammar nerds crazy because even major language institutions ca n't agree on whether it should be used .

what is the common wisdom for the comma ’ s usage ?

imagine a brilliant neuroscientist named mary . mary lives in a black and white room , she only reads black and white books , and her screens only display black and white . but even though she has never seen color , mary is an expert in color vision and knows everything ever discovered about its physics and biology . she knows how different wavelengths of light stimulate three types of cone cells in the retina , and she knows how electrical signals travel down the optic nerve into the brain . there , they create patterns of neural activity that correspond to the millions of colors most humans can distinguish . now imagine that one day , mary 's black and white screen malfunctions and an apple appears in color . for the first time , she can experience something that she 's known about for years . does she learn anything new ? is there anything about perceiving color that was n't captured in all her knowledge ? philosopher frank jackson proposed this thought experiment , called mary 's room , in 1982 . he argued that if mary already knew all the physical facts about color vision , and experiencing color still teaches her something new , then mental states , like color perception , ca n't be completely described by physical facts . the mary 's room thought experiment describes what philosophers call the knowledge argument , that there are non-physical properties and knowledge which can only be discovered through conscious experience . the knowledge argument contradicts the theory of physicalism , which says that everything , including mental states , has a physical explanation . to most people hearing mary 's story , it seems intuitively obvious that actually seeing color will be totally different than learning about it . therefore , there must be some quality of color vision that transcends its physical description . the knowledge argument is n't just about color vision . mary 's room uses color vision to represent conscious experience . if physical science ca n't entirely explain color vision , then maybe it ca n't entirely explain other conscious experiences either . for instance , we could know every physical detail about the structure and function of someone else 's brain , but still not understand what it feels like to be that person . these ineffable experiences have properties called qualia , subjective qualities that you ca n't accurately describe or measure . qualia are unique to the person experiencing them , like having an itch , being in love , or feeling bored . physical facts ca n't completely explain mental states like this . philosophers interested in artificial intelligence have used the knowledge argument to theorize that recreating a physical state wo n't necessarily recreate a corresponding mental state . in other words , building a computer which mimicked the function of every single neuron of the human brain wo n't necessarily create a conscious computerized brain . not all philosophers agree that the mary 's room experiment is useful . some argue that her extensive knowledge of color vision would have allowed her to create the same mental state produced by actually seeing the color . the screen malfunction would n't show her anything new . others say that her knowledge was never complete in the first place because it was based only on those physical facts that can be conveyed in words . years after he proposed it , jackson actually reversed his own stance on his thought experiment . he decided that even mary 's experience of seeing red still does correspond to a measurable physical event in the brain , not unknowable qualia beyond physical explanation . but there still is n't a definitive answer to the question of whether mary would learn anything new when she sees the apple . could it be that there are fundamental limits to what we can know about something we ca n't experience ? and would this mean there are certain aspects of the universe that lie permanently beyond our comprehension ? or will science and philosophy allow us to overcome our mind 's limitations ?

the mary 's room thought experiment describes what philosophers call the knowledge argument , that there are non-physical properties and knowledge which can only be discovered through conscious experience . the knowledge argument contradicts the theory of physicalism , which says that everything , including mental states , has a physical explanation . to most people hearing mary 's story , it seems intuitively obvious that actually seeing color will be totally different than learning about it .

which philosophical theory states that everything , including mental states , has a physical explanation ?

hmmm , that 's not what we want , is it ? today 's digital cameras do a lot for us , but there 's no replacement for the human eye . it 's important to learn how cameras work with light to create an image , that way we 'll know what 's going on when it 's time to capture a moment . there are three variables that determine if you 're getting the right amount of light for the correct exposure . with a manual camera , we 're able to change any of the variable ourselves . different settings can result in really different pictures . let 's look at the process together . first , see this here ? this is the aperture . it 's the hole that light passes through . if we make the aperture big , we 'll have more light , true , but the sharpness of your photo will decrease very quickly from your focus point , backward and forward . this is what we call shallow depth of field . if we have a very small aperture , we 'll have less light but a deeper depth of field . for portraits , it can be nice to have a sharp figure separate from a somewhat blurry background so i would suggest a large aperture . aperture is measured in f-stops . this can get a little confusing because lower numbers mean bigger apertures and higher numbers mean smaller apertures . next , there 's shutter speed to think about . the shutter acts like a curtain that covers the sensor , and it only opens when you release the shutter button . if we want less light , we open the shutter for a shorter time . if we want more light , we open it for a longer time , but we run the risk of getting a motion-blurred picture . the speed is measured in seconds and fractions of seconds . for shooting sports or anything with a lot of movement , we 'll need faster speeds . for taking awesome night landscapes , longer exposures will be better , but we 'll need a tripod to steady the shot and prevent motion blur . another cool thing we can do with light exposures is light painting , drawing in the dark with a torch or the light of a cell phone . lastly , iso sensitivity controls how sensitive the sensor is to light . if we use low sensitivity , we 'll need more light to register a photo . with a higher sensitivity , we 'll be able to get a picture with less available light . 100 iso is a low sensitivity , while 6400 iso is a high one . if we increase sensitivity , we 'll be able to use faster speeds and smaller apertures , but we 'll get noisier images . good thing we have something to tell us if we 're getting the correct amount of light to get a good exposure , the light meter . sound good to you ? now it 's time to get out there and practice taking pictures under different conditions , so you know what to do any time you want to take the best picture .

with a higher sensitivity , we 'll be able to get a picture with less available light . 100 iso is a low sensitivity , while 6400 iso is a high one . if we increase sensitivity , we 'll be able to use faster speeds and smaller apertures , but we 'll get noisier images .

which of these iso options will give us a noisier image ?

you may think you know the words that sit plainly in black on your page , but do n't be fooled . some words are capable of taking on different guises , masquerading as nouns , verbs and adjectives that alter their meanings entirely . this seeming superpower is called lexical ambiguity . it can turn words and sentences into mazes that mess with our minds . for example , consider the following : buffalo buffalo buffalo buffalo buffalo buffalo buffalo buffalo . that may sound like nonsense , but it 's actually a grammatically correct sentence . how ? well , buffalo is proper noun , a noun , and a verb . it refers to an animal also known as a bison , an american city , and it can also mean to bully . these different interpretations create a sequence of words that is grammatically correct as it stands , though it helps to add in a few implied phrases and punctuation marks to reveal what 's really going on . buffalo buffalo are bison from the city of buffalo , and this sentence has three groups of them . group a , which is bullied by group b , bullies group c. in other words , bison from buffalo that other bison from buffalo bully also bully bison from buffalo . if you let each buffalo perform its role , the meaning becomes apparent . what if the bunch of bullying buffalo decides to cross the ocean ? not just on any ship , but a ship-shipping ship shipping shipping-ships ? that sentence sounds just as outrageous , but there 's logic to the babble . ship can mean a vessel and to transport . when we sub in those meanings , a clearer picture emerges . here we have a huge ship-carrying vessel transporting ships that themselves are designed to carry goods across the sea . a ship-shipping ship , shipping shipping-ships . how about some entertainment on board this unusual vessel to offset the scuffling buffalo ? consider the can-can . can-can can-can can can can can can-can . here , the word can comes in many guises . there 's can-can , the flamboyant dance , can , that means able to , and can , figuratively meaning to outperform . by sticking in a comma and including the implied meanings , this sentence becomes clearer . can-can dances that can-can dances are able to outperform , can also outperform other can-can dances . you would n't necessarily use any of these sentences in a conversation . they 're just too ridiculous . yet they serve as an extreme example on just how tangled everyday language can be . lexical ambiguities sail into our speech and writing all the time , spreading confusion and misunderstanding wherever they can-can .

can-can can-can can can can can can-can . here , the word can comes in many guises . there 's can-can , the flamboyant dance , can , that means able to , and can , figuratively meaning to outperform .

sentences with one word never make any sense .

you might have seen this symbol before , whether it 's as a temporary tattoo or at a chinese temple . it 's called the yin-yang symbol . it comes from taoism , a religion born in china and it has far more meaning than you probably realize . the yin is the dark swirl , and the yang is the light one , and each side has a dot of the opposite color , which gives a clue to the meaning of yin and yang . everything contains the seed of its opposite . darth vadar has the seed of goodness , and luke has the potential to follow his father to the dark side . like luke and his father , yin and yang are not total opposites , they are relative to each other . taoists believe that the universe is made up of energies , vibrations , and matter , which behave differently in different contexts . something can be yin or yang depending on , well , depending on lots of things . so , while wheat that 's growing is yang , when it 's being reaped , it 's yin . a wave 's crest is yang , and the trough is yin . villages on the sunny side of a valley in china have names like liuyang or shiyang , but on the shady side , for example , of the yangtze river valley , there 's jiangyin . the brake is yin to the gas pedal 's yang . an eggshell is yang , the egg inside is yin . you think you 're getting it ? yang is harder , stronger , brighter , and faster , but one can turn into the other or are two sides of the same coin . the sunbeams are yang in comparison to the shadows . the pitch is yang , the catch is yin . the yang starts an action , and the yin receives it , completes it . yin is the inside space of a cup ; it would n't be a cup without it . yang is the cup . the coffee 's heat , however , is yang , and its blackness is yin . yang goes berserk sometimes , but there 's some very powerful yins , too , if they do n't quite go berserk . yin is the darker swirl , the female , but there is a white dot in it . and yang is the lighter , the male , but it has a black dot . water flowing calmly in a river is yin , but when it goes over the waterfall , it 's very yang . toothpicks are yin compared with a telephone pole . the back of a person is more yin than the front . the top of a person is the yang end . taoism teaches that there is a power in the universe . it 's higher , deeper , and truer than any other force . they call it the tao . it means the way . like the force in star wars , the tao has two sides . unlike other religions where the higher power is all good , and perhaps has an all-evil rival , taoism teaches that we need to learn from both yin and yang . and unlike religions with gods that are personal , the higher power in taoism is not . taoists believe that living in harmony with the way , a person will not have to fight against the universe 's natural flow . so , for example , listen more , argue less . be ready to back up or undo something , and you will make even faster progress . do n't worry about being the best , be who you are . live simply . complications take you away from the tao . `` the wise person is flexible , '' taoists say . learning to use the tao is what taoism is all about , and that 's why you should know your yin from your yang .

you might have seen this symbol before , whether it 's as a temporary tattoo or at a chinese temple . it 's called the yin-yang symbol . it comes from taoism , a religion born in china and it has far more meaning than you probably realize .

which part of a teacup is most yin ?

hey it 's me destin . welcome back to smarter every day . you 've heard people say , `` it 's just like riding a bike '' meaning it 's really easy and you ca n't forget how to do it , right ? but i did something . i did something that damaged my mind . it happened on the streets of amsterdam and i got really scared honestly . i ca n't ride a bike like you can anymore . before i show you the video of what happened i need to tell you the back story . like many six year olds with a macgyver mullet i learned how to ride a bike when i was really young . i had learned a life skill and i was really proud of it . everything changed though when my friend barney called me 25 years later . where i work , the welders are geniuses , and they like to play jokes on the engineers . he had a challenge for me . he had built a special bicycle and he wanted me to try to ride it . he had only changed one thing . when you turn the handlebar to the left , the wheel goes to the right . when you turn it to the right , the wheel goes to the left . i thought this would be easy so i hopped on the bike ready to demonstrate how quickly i could conquer this . - and here he is ladies and gentlemen , mr destin sandlin . first attempt riding the bicycle . - yeah , yeah . i could n't do it . you can see that i 'm laughing but i 'm actually really frustrated . in this moment i had a really deep revelation . my thinking was in a rut . this bike revealed a very deep truth to me . i had the knowledge of how to operate the bike , but i did not have the understanding . therefore , knowledge is not understanding . look i know what you 're probably thinking . destin 's probably just an uncoordinated engineer and ca n't do it . but that 's not the case at all . the algorithm that 's associated with riding a bike , in your brain , is just that complicated . think about it . downwards force on the pedals , leaning your whole body , pulling and pushing the handlebars , gyroscopic procession in the wheels , every single force is part of this algorithm . and if you change any one part it affects the entire control system . i do not make definitive statements that often , but i 'm telling you right now , you can not ride this bicycle . you might think you can , but you ca n't . i know this because i 'm often asked to speak at universities and conferences and i take the bike with me . it 's always the same . people think they 're gon na try some trick or they 're just gon na power through it . it does n't work . your brain can not handle this . for instance , this guy . i offered him two hundred dollars just to ride this bike ten feet across the stage . everybody thought he could do it . [ crowd exclaims ] no no no . you did n't understand . so.. this way , not that way . [ crowd laughs ] alright so , whenever you 're ready . remember you have to keep your feet on.. [ crowd laughs ] [ laughing crowd ] you 've got ta start rolling at least . and go . keep your feet on the pedal , go . [ laughing crowd ] just keep your feet on the pedals . alright , one more time . once you have a rigid way of thinking in your head , sometimes you can not change that , even if you want to . so here 's what i did . it was a personal challenge . i stayed out here in this driveway and i practiced about 5 minutes every day . my neighbors made fun of me . i had many wrecks . but after 8 months , this happened . one day i could n't ride the bike , and the next day i could . it was like i could feel some kind of pathway in my brain that was now unlocked . it was really weird though . it 's like there 's this trail in my brain , but if i was n't paying close enough attention to it , my brain would easily lose that neural path and jump back onto the old road it was more familiar with . any small distractions at all , like a cellphone ringing in my pocket , would instantly throw my brain back to the old control algorithm and i would wreck . but at least i could ride it . my son is the closest person to me genetically and he 's been riding a normal bike for 3 years , that 's over half his life . i wanted to know how long it would take him to learn how to ride a backwards bike so i told him if he learned how to ride a backwards bike he could go with me to australia and meet a real astronaut . are you gon na give up ? - no . - go ahead . this is how it starts . look at this . this is such a big deal . get up , you got it . did you see his brain get it ? so he , in.. how many weeks we been doing this ? two weeks ? in two weeks he did something that took me 8 months to do , which demonstrates that a child has more neural plasticity , am i even saying that right ? than an adult . it 's clear from this experiment that children have a much more plastic brain than adults . that 's why the best time to learn a language is when you 're a young child . alright , today 's bike log . i can ride smooth , i can ride fast . i 'm thinking the experiment is over . ok now i 'm in amsterdam , a city that has more bicycles than people . the question is , can i ride a normal bike now . i mean i have spent all this time unlearning how to ride a bike , if i go back and try to ride a normal one will my brain mess up . so i 've tweeted a smarter every day.. meetup , if you will . and i 'm gon na see if somebody brings a bicycle and i 'm gon na try to ride a normal bike . it 's backwards , it 's backwards . this was one of the most frustrating moments of my life . i had ridden a normal bike since i was six , but in this moment i could n't do it any more . i had set out to prove that i could free my brain from a cognitive bias , but at this point i 'm pretty sure that all i 've proved is that i can only re-designate that bias . so what you 're not seeing is there 's a group of people here , looking at me . looking at the strange american , that ca n't ride a bike , cause they think i 'm dumb . but i 'm actually two levels deep into this , because i 've learned and un-learned . alright . after 20 minutes of making a fool out of myself , suddenly my brain clicked back into the old algorithm . i ca n't explain it , but it happened in a very specific moment . [ laughter ] i 've got it , i 've got it , i 've got it . i 'm back . oh it clicked . it clicked . i 've got it , i 've got it . ok there it is . there was the moment . ok i can ride a bike . i tried to explain this to the people around me , and they just did n't get it . they thought i was faking the previous 20 minutes and i could n't get anybody to believe me . that looked like i faked it , did n't it . you think i 'm faking . you do n't believe me . - it looked so weird ... - you think i 'm lying do n't you . i 'm not lying . i felt like the only person on the planet who had ever un-learned how to ride a bike , and i could n't articulate it to anyone because everybody just knew that you ca n't forget how to ride a bike . so i learned 3 things from this experiment . i learned that welders are often smarter than engineers , i learned that knowledge does not equal understanding , and i learned that truth is truth . no matter what i think about it . so be very careful how you interpret things because you 're looking at the world with a bias whether you think you are or not . i 'm destin , you 're getting smarter every day , have a good one . ok if you wan na support smarter every day you can download a free audio book at audible.com/smarter i recommend commander hadfield 's book which is an astronaut 's guide to life on earth . i read it , it was awesome . if you think about it , i had to learn how to ride a different kind of bicycle and my son did it as well , but commander hadfield had to learn how to ride a different space ship . not only that , but a different type of space station . he was on mir and the international space station . anyway , if you 're interested in supporting smarter every day , audible.com/smarter , an astronaut 's guide to life on earth . i 'm destin , you 're getting smarter every day . have a good one . [ crowd cheers ] everything is wrong ... my instinctive reaction is wrong . ( destin ) why do n't you ride it ? you just build it ? - i ca n't ride it , i just build it . [ laughs ]

i had ridden a normal bike since i was six , but in this moment i could n't do it any more . i had set out to prove that i could free my brain from a cognitive bias , but at this point i 'm pretty sure that all i 've proved is that i can only re-designate that bias . so what you 're not seeing is there 's a group of people here , looking at me .

destin says that he set out to prove that he could free his brain from cognitive bias , but that instead he merely re-designated the bias . using the example of the backwards bicycle , explain what he means by this .

the evolutionary tango of animal genitalia . can you guess what you 're looking at ? if you answered `` duck vagina , '' you 'd be right . although the bird 's outward appearance may not strike you as especially odd , it uses this strange , intricate , cork-screw shaped contraption to reproduce . we see similarly unbelievable genitalia in insects , mammals , reptiles , fish , spiders , and even snails . apparently , no organs evolve faster and into more variable shapes than those involved in procreation . superficially , it makes sense because evolution works via reproduction . when an animal leaves more offspring , its genes will spread . and since genitalia are an animal 's tools for reproduction , any improvement there will have immediate effect . and yet , what 's the point of having such decorative nether regions ? after all , the function of genitalia seems simple . a penis deposits a bit of sperm and a vagina receives it and delivers it to the egg . a pipette-like thingy on the male and a funnel-like gizmo on the female should do just fine for any animal . and yet , that 's not what we see . the penis of a chicken flea , for example , looks nothing like a pipette , more like an exploded grandfather clock . and the vagina of a featherwing beetle resembles something you 'd find in a dr. seuss book . throughout the animal kingdom , genitalia are very complex things , much more complicated than seems necessary for what they 're meant to do . that 's because genitalia do more than just deposit and receive sperm . many male animals also use the penis as courtship device , like crane flies . in some south american species , males have a tiny washboard and scraper on their penis , which produces a song that reverberates throughout the female 's body when they mate . it 's thought that if female crane flies enjoy this unusual serenade , they 'll allow the male to father their offspring . this way , the genes of the most musical penises spread , leading to rapid evolution of insects ' phalluses . similarly , some beetles have two little drumsticks on either side of the penis . during mating , they 'll rub , slap , or tap the female with these . and some hoofed mammals , like rams and bulls , use a whip-like extension on the penis 's left side to create a sensation during mating . but how can females really choose between males if she can only assess them after mating ? this is where the power of female adaptation comes into play . in fact , insemination is different to conception , and the female genitalia exploit this distinction . for instance , in some dung flies , the vagina contains pockets for separating sperm from different males depending on how appealing they were . males using their penises for courtship and females controlling their own sperm management are two reasons why genitalia evolve into such complex shapes . but there are others because genitalia are also where a sexual conflict is played out . a female 's interests are best served if she fertilizes her eggs with the sperm of the best fathers and creates genetic variability amongst her offspring . for a male , on the other hand , this is bad news . for him , it would be best if a female used his sperm to fertilize all of her eggs . so we see cycles of adaptation in an evolutionary arms race to retain control . black widow spiders have a disposable penis tip that breaks off inside the vagina blocking the attempts of his rivals , and bed bug males bypass a female 's genitalia altogether using a syringe-like penis to inject sperm cells directly into her belly . not to be outdone , females have evolved their own countermeasures . in some bed bug species , the females have evolved an entirely new set of genitalia on their right hand flanks where the males usually pierce them . that allows them to maintain the power to filter out unwanted sperm with their genitalia . and duck vaginas are shaped like a clockwise spiral so that when the male inflates his long , counterclockwise coiled penis into her , and she disapproves , all she needs to do is flex her vaginal muscles and the penis just flubs out . so , genitalia differs so much , not just to fascinate us , but because in every species , they 're the result of a furious evolutionary tango of sex that has been going on for millions of years and will continue for millions of years to come .

for a male , on the other hand , this is bad news . for him , it would be best if a female used his sperm to fertilize all of her eggs . so we see cycles of adaptation in an evolutionary arms race to retain control .

how can female dung flies decide which males will fertilize her eggs after she has mated with them ?

hafnium is , i think , an element to watch . at the moment , it does not have many uses but there is a strong opinion that hafnium is going to be used in making layers on computer chips like this , and that hafnium oxide will have better properties than some of the other oxides that are used . so i think that hafnium is certainly something that ’ s way up on the charts and soon may be much higher than its existing number on the periodic table - in the elements popularity .

hafnium is , i think , an element to watch . at the moment , it does not have many uses but there is a strong opinion that hafnium is going to be used in making layers on computer chips like this , and that hafnium oxide will have better properties than some of the other oxides that are used . so i think that hafnium is certainly something that ’ s way up on the charts and soon may be much higher than its existing number on the periodic table - in the elements popularity .

which is hafnium´s preferred oxidation state when forming compounds , such as its oxide ?

you 're swimming in the ocean when something brushes your leg . when the tingling sets in , you realize you 've been stung by a jellyfish . how do these beautiful , gelatinous creatures pack such a painful punch ? jellyfish are soft because they are 95 % water and are mostly made of a translucent gel-like substance called mesoglea . with such delicate bodies , they rely on thousands of venom-containing stinging cells called cnidocytes for protection and prey capture . even baby jellyfish , the size of a pencil eraser , have the ability to sting . larval jellyfish , ephyrae , look like tiny flowers pulsating in the sea . as they grow , they become umbrella-shaped with a bell at the top and descending tentacles around the margin . the largest species of jellyfish , the lion 's mane , has tentacles that can extend more than 100 feet , longer than a blue whale . these tentacles contain most of the stinging cells , although some species have them on their bells , too . venom is ejected via a nematocyst , a whip-like hollow tubule , which lies coiled under high osmotic pressure . when mechanical or chemical stimuli activate an external trigger , the lid of the cell pops open and sea water rushes in . this forces a microscopic barbed harpoon to shoot out , penetrate and inject venom into its victim . nematocyst discharge can occur in less than a millionth of a second , making it one of nature 's fastest biomechanical processes . nematocysts can continue to fire even after a jellyfish has died , so it 's important to remove lingering tentacles stuck to the skin . rinsing with vinegar will usually render undischarged nematocysts inactive . seawater can also help remove residual nematocysts . but do n't use fresh water because any change in salt balance alters the osmotic pressure outside of the cnidocyte and will trigger the nematocyst to fire . that 's why urinating on the affected area , a common folk remedy , may do more harm that good , depending on the composition of the urine . most jellyfish stings are a painful nuisance , but some can be deadly . an indo-pacific box jelly , also called a sea wasp , releases venom which can cause contraction of the heart muscles and rapid death in large doses . there 's an anti-venom , but the venom is fast-acting , so you 'd need immediate medical intervention . despite the impressive power in their tentacles , jellies are n't invincible . their stinging cells are no match for the armor of thick-skin predators , like the leatherback turtle and ocean sunfish . these predators both have adaptations that prevents slippery jellyfish from escaping after they are engulfed : backwards pointing spines in the turtle 's mouth and esophagus and recurved teeth behind the sunfish 's cheeks . even tiny lobster slipper larvae can cling to the bell of a jellyfish and hitch a ride , snacking on the jelly while they preserve their own energy for growth . small agile fish use the jellies as moving reefs for protection , darting between tentacles without ever touching them . nudibranchs , which are sea slugs covered in protective slime , can actually steal the jelly 's defenses by eating the cnidocytes and transferring them to specialized sacks for later use , as weapons against their own predators . even humans might benefit from the sting of a jellyfish one day . scientists are working on manipulating cnidocytes to deliver medicine , with nematocysts rarely 3 % of the size of a typical syringe needle . so , the next time you 're out in the ocean , be careful . but also , take a second to marvel at its wonders .

how do these beautiful , gelatinous creatures pack such a painful punch ? jellyfish are soft because they are 95 % water and are mostly made of a translucent gel-like substance called mesoglea . with such delicate bodies , they rely on thousands of venom-containing stinging cells called cnidocytes for protection and prey capture .

jellyfish are mostly made of :

there is a curse that has plagued humanity since ancient times . the greeks fought it by chewing aromatic resins , while the chinese resorted to egg shells . in the ancient jewish talmud , it 's even considered legal grounds for divorce . this horrible scourge is halitosis , otherwise known as bad breath . but what causes it , and why is it so universally terrifying ? well , think of some of the worst odors you can imagine , like garbage , feces or rotting meat . all of these smells come from the activity of microorganisms , particularly bacteria , and , as disgusting as it may sound , similar bacteria live in the moisture-rich environment of your mouth . do n't panic . the presence of bacteria in your body is not only normal , it 's actually vital for all sorts of things , like digestion and disease prevention . but like all living things , bacteria need to eat . the bacteria in your mouth feed off of mucus , food remnants , and dead tissue cells . in order to absorb nutrients through their cell membranes , they must break down the organic matter into much smaller molecules . for example , they 'll break proteins into their component amino acids and then break those down even further into various compounds . some of the foul-smelling byproducts of these reactions , such as hydrogen sulfide and cadaverine , escape into the air and waft their way towards unsuspecting noses . our sensitivity to these odors and interpretation of them as bad smells may be an evolutionary mechanism warning us of rotten food and the presence of disease . smell is one of our most intimate and primal senses , playing a huge role in our attraction to potential mates . in one poll , 59 % of men and 70 % of women said they would n't go on a date with someone who has bad breath , which may be why americans alone spend $ 1 billion a year on various breath products . fortunately , most bad breath is easily treated . the worst smelling byproducts come from gram-negative bacteria that live in the spaces between gums and teeth and on the back of the tongue . by brushing and flossing our teeth , using antibacterial mouthwash at bedtime , gently cleaning the back of the tongue with a plastic scraper and even just eating a healthy breakfast , we can remove many of these bacteria and their food sources . in some cases , these measures may not be enough due to dental problems , nasal conditions , or rarer ailments , such as liver disease and uncontrolled diabetes . behaviors like smoking and excessive alcohol consumption also have a very recognizable odor . regardless of cause , the bad smell almost always originates in the mouth and not the stomach or elsewhere in the body . but one of the biggest challenges lies in actually determining how our breath smells in the first place , and it 's unclear why . it may be that we 're too acclimatized to the smell inside our own mouths to judge it . and methods like cupping your hands over your mouth , or licking and smelling your wrist do n't work perfectly either . one study showed that even when people do this , they tend to rate the smell subjectively according to how bad they thought it was going to be . but there 's one simple , if socially difficult , way of finding out how your breath smells : just take a deep breath and ask a friend .

in one poll , 59 % of men and 70 % of women said they would n't go on a date with someone who has bad breath , which may be why americans alone spend $ 1 billion a year on various breath products . fortunately , most bad breath is easily treated . the worst smelling byproducts come from gram-negative bacteria that live in the spaces between gums and teeth and on the back of the tongue .

bad breath improves when you _____ .

translator : andrea mcdonough reviewer : bedirhan cinar people often think the word `` doubt '' spelling is a little crazy because of the letter `` b '' . since it does n't spell a sound , most folks ca n't figure out what it 's doing there . but in spite of what most of us learn in school , sound is < i > never < /i > the most important aspect of spelling an english word . a word 's meaning and history need to come first . to doubt means to question , to waver , to hesitate . as a noun , it means uncertainty or confusion . the present-day english word `` doubt '' started as a latin word , `` dubitare '' . it first moved from latin into french where it lost both its `` buh '' sound and its letter `` b '' . and then it came into english in the 13th century . about 100 years later , scribes who wrote english but also knew latin , started to reinsert the `` b '' into the word 's spelling , even though no one pronounced it that way . but why would they do this ? why would anyone in their right mind reinsert a silent letter into a spelling ? well , because they knew latin , the scribes understood that the root of `` doubt '' had a `` b '' in it . over time , even as fewer literate people knew latin , the `` b '' was kept because it marked important , meaningful connections to other related words , like `` dubious '' and `` indubitalbly , '' which were subsequently borrowed into english from the same latin root , `` dubitare '' . understanding these historical connections not only helped us to spell `` doubt , '' but also to understand the meaning of these more sophisticated words . but the story does n't end there . if we look even deeper , we can see beyond the shadow of a doubt , just how revealing that `` b '' can be . there are only two base words in all of english that have the letters `` d-o-u-b '' : one is doubt , and the other is double . we can build lots of other words on each of these bases , like doubtful and doubtless , or doublet , and redouble , and doubloon . it turns out that if we look into their history , we can see that they both derive from the same latin forms . the meaning of double , two , is reflected in a deep understanding of doubt . see , when we doubt , when we hesitate , we second guess ourselves . when we have doubts about something , when we have questions or confusion , we are of two minds . historically , before english began to borrow words from french , it already had a word for doubt . that old english word was `` tweogan , '' a word whose relationship to `` two '' is clear in its spelling as well . so the next time you are in doubt about why english spelling works the way it does , take a second look . what you find just might make you do a double-take .

as a noun , it means uncertainty or confusion . the present-day english word `` doubt '' started as a latin word , `` dubitare '' . it first moved from latin into french where it lost both its `` buh '' sound and its letter `` b '' .

why does the word doubt contain a silent `` b '' ?

translator : andrea mcdonough reviewer : bedirhan cinar it is only in the last 100 or so years that human kind has understood that the nucleus of the chemical elements is not always fixed . it can change spontaneously from one element to another . the name for this process is radioactivity . you probably already know something about the nucleus : it 's much tinier than the atom , it 's made of particles called protons and neutrons , there are electrons orbiting around it . and though the atoms can share or swap electrons when they bond together , the nuclei themselves never change . right ? well , no . certain nuclei are not stable in that way . this means they may change suddenly , spontaneously . the radioactive nucleus flings out a small particle and transforms into another element , just like that . for example , the carbon nucleus can eject a fast-moving electron and turn into a nitrogen nucleus . there are two different particles that can be emitted from radioactive nuclei , but never together . the very fast electron is known as a beta particle . if you know a little bit about electrons , you may be thinking , `` what was the electron doing in the nucleus in the first place ? '' the answer is there is a neutron in nucleus spontaneously changed into a proton , which stayed behind , and the electron flew out as a beta particle . this is not what chemistry has taught us to expect . the nucleus is supposed to be stable . neutrons do n't change into protons . except , sometimes they do ! the other particle it emits spontaneously from an unstable nucleus is alpha . an alpha particle is 8,000 times more massive than beta , and it 's a bit slower . alpha is made from two protons and two neutrons . if we trap all those alpha particles together , we get helium gas . alpha is a helium nucleus . like the beta particle , you would not have expected a heavier nucleus to throw out helium . but again , it happens , and the nucleus becomes a new element . so , is radioactivity useful or just dangerous ? wherever you are sitting , it is quite likely that there is a device nearby which contains a source of alpha particles : a smoke detector . the source is radioactive americium . you are totally safe from these alpha particles , which can not travel more than a few centimeters in air . beta particles penetrate much farther through materials than alpha can . radioactive atoms are used in medicine as traces , to show where chemicals travel in the patient . beta particles are emitted and have enough energy to emerge from the body and be detected . there is a third type of nuclear radiation : gamma , which is not a particle at all . it is an electromagnetic wave , like microwaves , or light , but it is actually 1,000 times more energentic than visible light . gamma rays may pass right through your body . gamma is used to zap the bacteria in fruit to increase its shelf life , or in radiotherapy to kill cancer cells . radioactive substances get hot , and this heat can be used to generate power . this heat has been brought to you since space probes , and , in the past , in pacemakers for hearts . the more abruptly nuclear radiation is slowed down , the more damage it does to the atoms it hits . this is called ionization . alpha causes the most ionization as it crashes into other atoms and gamma the least . in humans , the most serious effect of radiation is the damage that it can cause to our dna . although alpha can not penetrate your skin , if you inhale or injest a radioactive nucleus , the health consequences can be severe . radioactivity is both useful and deadly , but it is all around us as a background to the natural world .

well , no . certain nuclei are not stable in that way . this means they may change suddenly , spontaneously .

imagine a source containing 8 million radioactive nuclei . for this particular material , in one hour , half of the nuclei decay . thus , after one hour , 4 million nuclei have decayed and there are 4 million remaining . write down the numbers of nuclei remaining after each subsequent hour for the next four hours . use the numbers to sketch a graph of ‘ number of remaining nuclei ’ against ‘ time in hours ’ . this is the characteristic shape of exponential decay .

translator : andrea mcdonough reviewer : jessica ruby mysteries of vernacular : fizzle , to end weakly or to fail , to die out . the definition of fizzle likely links back to the old english word fist , which meant stink . in the mid-fifteenth century , fist developed into the verb fisten , to break wind , which eventually lead to the modern word feisty , but that 's another story . in its earliest form , as a variant of fisten , fizzle had a very specific meaning : to break wind without noise . surprisingly , considering this initial definition , by the 1800s , the word fizzle referred instead to a specific sound , rather graphically , to the sputtering or hissing of a gas or liquid being forced out of a narrow opening . the figurative sense of the word , a weak ending , is thus understandable within the context of a flame consuming the last drops of oil in a lantern or a valve drawing out the contents of the bottom of a cask . though perhaps not derived directly from this subsiding verb , our modern meaning of fizzle developed as slang in the 1800s . originally used on college campuses to describe failure , specifically on an exam , it was n't long before the word came to mean exactly what it does today and was quickly and widely adopted .

in the mid-fifteenth century , fist developed into the verb fisten , to break wind , which eventually lead to the modern word feisty , but that 's another story . in its earliest form , as a variant of fisten , fizzle had a very specific meaning : to break wind without noise . surprisingly , considering this initial definition , by the 1800s , the word fizzle referred instead to a specific sound , rather graphically , to the sputtering or hissing of a gas or liquid being forced out of a narrow opening .

why do you think the original definition of fizzle ( “ to break wind without noise ” ) is no longer used ?